prima: Fix possible OOB read in ProcDnldRsp

In ProcDnldRsp, pHdr->sBufSize is coming from fw message
which could not be trusted. Before its use ProcDnldRsp
should verify it against its max allowed size (UINT_MAX).

Fix is to add a sanity check for pHdr->sBufSize against
UINT_MAX before its use.

Change-Id: I6ec970483af860d5e42d6adac640274743f44f1a
CRs-Fixed: 2347297