Changes to support topology and port speed agnostic switch init for TD3 based platforms (#10587)

Author: vmittal-msft

device/arista/x86_64-arista_7050cx3_32s/Arista-7050CX3-32S-C32/td3-a7050cx3-32s-32x100G.config.bcm

@@ -52,7 +52,7 @@ stable_size=0x5500000
 tdma_timeout_usec=15000000
 tslam_timeout_usec=15000000
 sai_optimized_mmu=1
-mmu_init_config="TD3-MSFT-T0-100G"
+mmu_init_config="TD3-MSFT-CUSTOM"
 buf.map.egress_pool0.ingress_pool=0
 buf.map.egress_pool1.ingress_pool=0
 buf.map.egress_pool2.ingress_pool=1

device/arista/x86_64-arista_7050cx3_32s/Arista-7050CX3-32S-D48C8/td3-a7050cx3-32s-48x50G+8x100G.config.bcm

@@ -52,7 +52,7 @@ stable_size=0x5500000
 tdma_timeout_usec=15000000
 tslam_timeout_usec=15000000
 sai_optimized_mmu=1
-mmu_init_config="TD3-MSFT-T0-50G"
+mmu_init_config="TD3-MSFT-CUSTOM"
 buf.map.egress_pool0.ingress_pool=0
 buf.map.egress_pool1.ingress_pool=0
 buf.map.egress_pool2.ingress_pool=1