msm: kgsl: Move globals to the KGSL device handle

Move the list of globals out of iommu and move them to a linked list in
the device instead. But that's not the clever part. The clever part is
we painstakingly dynamically allocate all of the global objects and
track them so we can automatically clean them up when the device is
removed, thereby saving quite a bit of pain. Also, by dynamically
allocating the memdescs we can skip creating lots of static memory
descriptors that may or may not be used for any given target.

Change-Id: Ic0dedbadb9963bb7395a9845aebc1d828ba6dd8e
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>