[Mellanox] Add KV to SN5640-SIMx sai.profile (#21365)

- Why I did it
Add SAI_KEY_SPC5_LOSSY_SCHEDULING=1 and
SAI_DEFAULT_SWITCHING_MODE_STORE_FORWARD=1
to SN5640-simx sai.profile, to support those features in the SKU

- How I did it
Added parameters to file

- How to verify it
Deploy SKU and check SAI logs

Author: noaOrMlnx

device/mellanox/x86_64-nvidia_sn5640_simx-r0/ACS-SN5640/sai.profile

@@ -1 +1,4 @@
 SAI_INIT_CONFIG_FILE=/usr/share/sonic/hwsku/sai_5640.xml
+SAI_KEY_SPC5_LOSSY_SCHEDULING=1
+SAI_DEFAULT_SWITCHING_MODE_STORE_FORWARD=1
+