msm: kgsl: Cleanup a superfluous structure in kgsl_device.h

struct kgsl_memregion was used to store the MMIO and GMEM
addressing for KGSL and adreno but it didn't serve much
purpose other than another level of redirection in the
structures.  Remove it and add the necessary pointer and
size members directly to the KGSL and adreno structs.

Change-Id: Ic0dedbad8ec3f0a2c63383fa451cc39a25cab087
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>