msm: kgsl: Enable "big page" memory allocations

Allow users to specify "big page" mode when allocating GPU
memory. This will attempt to allocate contigious units of 64k
bytes per instead of the usual PAGE_SIZE units.  If the allocation
fails, then automatically fall back to allocate the rest of the
region with 4K pages. This means that potentially any allocation
could be comprised of a mixture of 64k chunks and 4k chunks.

Change-Id: Ic0dedbadcf1f4b30a106f430dd2d87781ea54829
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>