[sonic-utilities] Submodule update (#8338)

This PR contains the following commits:
54b74a2 2021-08-04 [LLDP] Fix lldpshow script to enable display multiple MAC addresses on the same remote physical interface (#1657)
0d53b7a 2021-08-03 [sonic_installer] don't print errors when installing an image not supporting app ext (#1719)
394e2fb 2021-08-03 Implement script null_route_helper (#1737)
dd01b56 2021-08-02 disk_check updates: (#1736)
8a74d03 2021-07-30 [CLI][show][bgp] Fix the show ip bgp network command (#1733)
679a4ba 2021-07-30 [MACsec]: Allow upgrade-docker for macsec container (#1716)
e9c73e8 2021-07-28 [CLI][MPLS][Show] Added multi ASIC support for 'show mpls command'.


Signed-off-by: Basim Shalata <basims@nvidia.com>