platform-mc: fix double header subtraction in getFRURecordTable

The responseLen returned by sendRecvPldmMsg is already payload-only.
Subtracting sizeof(pldm_msg_hdr) again in getFRURecordTable caused the
last 3 bytes of the FRU record table data to be silently truncated.

Remove the redundant sizeof(pldm_msg_hdr) subtraction to match the
convention used by all other decode calls in platform_manager.cpp.

Fixes: b6d3943 ("platform-mc: discovery FRU data from terminus")
Change-Id: I748bc5993f9aa66e11f1ee699478ad1fd3558bda
Co-developed-by: Arun P. Mohanan <arun.p.m@intel.com>
Signed-off-by: Vishnunithyasoundhar S <vishnunithyasoundhar.s@intel.com>

platform-mc/platform_manager.cpp

diff --git a/platform-mc/platform_manager.cpp b/platform-mc/platform_manager.cpp
index 234e117..9d9338c 100644
--- a/platform-mc/platform_manager.cpp
+++ b/platform-mc/platform_manager.cpp
@@ -778,8 +778,8 @@
 
     auto responsePtr = reinterpret_cast<const struct pldm_msg*>(responseMsg);
     rc = decode_get_fru_record_table_resp(
-        responsePtr, responseLen - sizeof(pldm_msg_hdr), &completionCode,
-        nextDataTransferHndl, transferFlag, recordData.data(), responseCnt);
+        responsePtr, responseLen, &completionCode, nextDataTransferHndl,
+        transferFlag, recordData.data(), responseCnt);
 
     if (rc)
     {