msm: kgsl: Use system memory for kernel globals

Kernel global GPU memory usually lasts for the life of the driver. It
doesn't make any sense to take them out of the KGSL pool since they will
never be recycled.  Add a flag to allocate 4k pages from system memory
and use them by default for global objects.

Change-Id: Ic0dedbadd0ff1f558d5f9711ec9843451593aee4
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>