[Mellanox]Updating SAI profile with WECMP Normalization setting (#20623)

- Why I did it
Setting the KV attribute for WECMP normalization

- How I did it
Update common sai.profile

- How to verify it
Running basic WECMP tests.

platform/mellanox/docker-syncd-mlnx/sai-common.profile

@@ -5,3 +5,4 @@ SAI_KEY_SDK_SNIFFER_MODE=cyclic
 SAI_KEY_SDK_SNIFFER_LOG_NUM=10
 SAI_KEY_SDK_SNIFFER_LOG_MAX_SIZE=314572800
 SAI_KEY_SDK_SNIFFER_WRITE_INTERVAL=1000
+SAI_WCMP_NORMALIZATION_MAX_TOTAL_WEIGHT=256