msm: kgsl: In snapshot skip object if it is in ib list

When looking for objects to save in snapshot, check whether the
object is already tracked in the ib list first. If it is tracked
there then skip tracking the object as it is already tracked.

Change-Id: Ife408ad16b86482a12e7d9e53a243505451d7fdc
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>