msm: kgsl: Unprotect the VBIF performance counters

The A3XX protected mode registers are too broad and are protecting
the VBIF performance counters by accident.  Dial back the protection
to just the VBIF configuration registers.

CRs-fixed: 554672
Change-Id: Ic0dedbad210a548a11c953c7601144786174081b
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>