msm: kgsl: Use a bitmap allocator for global addressing

To prepare to allow global buffers to allocate a semi-random GPU address
move from a sequential allocator to a bitmap based one.

Change-Id: Ic0dedbadba36c4c7b7839528103997724eac7d6d
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>