msm: kgsl: Defer drawobj_sync_timeline_fence_work() to a workqueue

drawobj_sync_timeline_fence_work() does a cleanup of fence and syncobj
allocations. Doing this cleanup in irq context requires the irq_work
struct to remain valid after the function executes. Avoid this constraint
by deferring this work to the memory workqueue.

Change-Id: Icf648a61686c1ef3fd84467a2376b11a9a4bb803
Signed-off-by: Lynus Vaz <[email protected]>