msm: kgsl: Don't allocate SVM addresses inside the global range

If MAP_FIXED is specified when mmap()ing SVM buffers we try to honor that
request even if it falls outside of the defined SVM range.  The notable
exception is the global buffer range. Attempt no landings there.

Change-Id: Ic0dedbada933691e28a2f9b2c0fe5e25ba69e5be
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>