msm: kgsl: clean up iommu/gpummu protflag handling

Make kgsl_memdesc_protflags() return the correct type of flags
for the type of mmu being used. Query the memdesc with this
function in kgsl_mmu_map(), rather than passing in the
protflags. This prevents translation at multiple layers of
the code and makes it easier to enforce that the mapping matches
the allocation flags.

Change-Id: I2a2f4a43026ae903dd134be00e646d258a83f79f
Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>
diff --git a/drivers/gpu/msm/adreno_ringbuffer.c b/drivers/gpu/msm/adreno_ringbuffer.c
index 282b986..96e13c4 100644
--- a/drivers/gpu/msm/adreno_ringbuffer.c
+++ b/drivers/gpu/msm/adreno_ringbuffer.c
@@ -480,6 +480,7 @@
 	 */
 	rb->sizedwords = KGSL_RB_SIZE >> 2;
 
+	rb->buffer_desc.flags = KGSL_MEMFLAGS_GPUREADONLY;
 	/* allocate memory for ringbuffer */
 	status = kgsl_allocate_contiguous(&rb->buffer_desc,
 		(rb->sizedwords << 2));