qcacmn: Validate the rx descriptor before dereferencing

The rx descriptor obtained using the cookie
can be NULL if the cookie is invalid. Hence
dereferencing the rx descriptor without any
validation can cause invalid address access.

Fix this by validating the rx descriptor
which has been obtained using the cookie from
the hal ring descriptor.

Change-Id: Ib584f0d8175b581d15b0e1c67d2f6ed9119ecbfc
CRs-Fixed: 2629254
3 files changed