msm: kgsl: Fix memory leak of DRM GEM object structure.
This changes frees the DRM GEM object structure in
kgsl_gem_free_object function. kgsl_gem_free_object is
called from DRM module after the last refrence to the
object has been lost.

Change-Id: I21d91e9706cf46909168ab99b130ef4d833886e6
Signed-off-by: Hareesh Gundu <hareeshg@codeaurora.org>