for fixing centec-arm64 compile error (#11186)

Why I did it
Fix Centec-Arm64 compile error, Centec SAI Dev package reference is error

How I did it
Modify sai.mk of arm64 platform for Centec

How to verify it
Build centec amd64 and arm64 sonic image

platform/centec-arm64/sai.mk

@@ -5,7 +5,7 @@ export CENTEC_SAI = libsai_$(CENTEC_SAI_VERSION)_$(PLATFORM_ARCH).deb
 export CENTEC_SAI_DEV = libsai-dev_$(CENTEC_SAI_VERSION)_$(PLATFORM_ARCH).deb
 
 $(CENTEC_SAI)_URL = https://github.com/CentecNetworks/sonic-binaries/raw/master/$(PLATFORM_ARCH)/sai/$(CENTEC_SAI)
-$(CENTEC_SAI)_DEV_URL = https://github.com/CentecNetworks/sonic-binaries/raw/master/$(PLATFORM_ARCH)/sai/$(CENTEC_SAI_DEV)
+$(CENTEC_SAI_DEV)_URL = https://github.com/CentecNetworks/sonic-binaries/raw/master/$(PLATFORM_ARCH)/sai/$(CENTEC_SAI_DEV)
 $(eval $(call add_conflict_package,$(CENTEC_SAI_DEV),$(LIBSAIVS_DEV)))
 
 SONIC_ONLINE_DEBS += $(CENTEC_SAI)