[Mellanox] fix new MSN2700-A1 platform name (#17151)

- Why I did it
New introduced MSN2700 platform has a different platform name compared to the old one, it should be "MSN2700-A1".

- How I did it
Update the name to the new one in platform.json and platform_components.json.

- How to verify it
run platform-related sonic-mgmt test cases on the new platform.

Signed-off-by: Kebo Liu <kebol@nvidia.com>

device/mellanox/x86_64-mlnx_msn2700a1-r0/platform.json

@@ -1,6 +1,6 @@
 {
     "chassis": {
-        "name": "MSN2700",
+        "name": "MSN2700-A1",
         "components": [
             {
                 "name": "ONIE"

device/mellanox/x86_64-mlnx_msn2700a1-r0/platform_components.json

@@ -1,6 +1,6 @@
 {
     "chassis": {
-        "MSN2700": {
+        "MSN2700-A1": {
             "component": {
                 "ONIE": { },
                 "SSD": { },