msm: kgsl: Convert cache invalidate operations to flush for ARM64

ARM64 does not allow invalidate only operations on read-only pages.
Since invalidate only operations aren't really useful on user
mapped pages anyway we can get away with translating invalidate
requests into flush operations.

Change-Id: Ic0dedbadc8522c49f62ef0fd6d4264a026273eda
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>