With Broadcom SAI 4.2, setting buffer profile dynamic threshold will cause SAI to crash

[yxieca]

Description
With Broadcom SAI 4.2, setting buffer profile dynamic threshold will cause SAI to crash

Steps to reproduce the issue:
There are 2 ways to repeat this issue:

1. sudo mmuconfig -p egress_lossy_profile -a 0
2. with latest image, warm reboot.

Describe the results you received:
Jan 5 17:15:11.286647 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1103 Obtained 17 stack frames.
Jan 5 17:15:11.286647 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/lib/libsai.so.1(_brcm_sai_log_backtrace+0x21) [0x7f5554b1b2d1]
Jan 5 17:15:11.286647 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/lib/libsai.so.1(_brcm_sai_switch_assert+0x31) [0x7f55549f6751]
Jan 5 17:15:11.286647 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/lib/libsai.so.1(_brcm_sai_indexed_data_get+0x1b34) [0x7f5554b6e2f4]
Jan 5 17:15:11.286647 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/lib/libsai.so.1(_brcm_sai_switch_port_queue_get+0x64) [0x7f55549fcb34]
Jan 5 17:15:11.286647 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/lib/libsai.so.1(driverEgressQueueFieldSet+0x78) [0x7f55564cf198]
Jan 5 17:15:11.286647 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/lib/libsai.so.1(+0x22c651c) [0x7f5554a7f51c]
Jan 5 17:15:11.286647 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/bin/syncd(+0x918e1) [0x55859f0118e1]
Jan 5 17:15:11.286647 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/bin/syncd(+0x24b76) [0x55859efa4b76]
Jan 5 17:15:11.286647 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/bin/syncd(+0x2aee5) [0x55859efaaee5]
Jan 5 17:15:11.287069 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/bin/syncd(+0x323ee) [0x55859efb23ee]
Jan 5 17:15:11.287069 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/bin/syncd(+0x33646) [0x55859efb3646]
Jan 5 17:15:11.287069 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/bin/syncd(+0x33954) [0x55859efb3954]
Jan 5 17:15:11.287069 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/bin/syncd(+0x34ba8) [0x55859efb4ba8]
Jan 5 17:15:11.287095 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/bin/syncd(+0x21b38) [0x55859efa1b38]
Jan 5 17:15:11.287095 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/bin/syncd(+0x200de) [0x55859efa00de]
Jan 5 17:15:11.287095 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xeb) [0x7f555223109b]
Jan 5 17:15:11.287109 str-7260cx3-acs-1 CRIT syncd#syncd: [0] SAI_API_SWITCH:_brcm_sai_log_backtrace:1106 /usr/bin/syncd(+0x2177a) [0x55859efa177a]

Describe the results you expected:
Setting mmucongif success and warm reboot success.

Additional information you deem important (e.g. issue happens only occasionally):

**Output of `show version`:**

```

SONiC Software Version: SONiC.master.540-dirty-20210101.084606
Distribution: Debian 10.7
Kernel: 4.19.0-9-2-amd64
Build commit: a165e63
Build date: Fri Jan 1 08:59:09 UTC 2021
Built by: johnar@jenkins-worker-8
```