msm: kgsl: Pad sparse objects when mapping them

The device may require a minimum alignment and padding for GPU VA
mappings. Pad sparse objects up to this alignment when mapping them.

Change-Id: I807eec24a3b4adbfcb1aa8347783a61ed70d355b
Signed-off-by: Lynus Vaz <lvaz@codeaurora.org>