qcacmn: qdf: Replace explicit comparison to NULL

Per the Linux Kernel coding style, as enforced by the kernel
checkpatch script, pointers should not be explicitly compared to
NULL. Therefore within qdf replace any such comparisons with logical
operations performed on the pointer itself.

Change-Id: Ie7662617dad8138b803dc54e7759d3b6d76c53ce
CRs-Fixed: 2418255
8 files changed