msm2: kgsl: Fix overflow check in mmap_range_valid

A eager compiler might optimize out the overflow check in
mmap_range_valid.  Add a check against ULONG_MAX to ensure
that the check is performed.

CRs-fixed: 546373
Change-Id: Ic0dedbad478cc3bd65a00a7b31d2039095c005d6
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
msm2: kgsl: Fix mem leak when page allocation fails

Page allocation may fail during OOM condition. Update
sglen and size to correct value (allocated) so that
they get freed in kgsl_sharedmem_free().

Change-Id: I1aa0ca77bb767523dfcf0f6cc3a21eac2b6b80e4
Signed-off-by: Hareesh Gundu <hareeshg@codeaurora.org>