drm/msm/sde: release the fence through kfree instead of kfree_rcu

The kfree_rcu free is not required after optimization in fence
driver with commit fd277cec ("drm/msm/sde: avoid spinlock
recursion in sde fence"). The sde fence can be released
immediately because it does not hold any refcount to any
of fence object.

Change-Id: If1df4ed3519a3f7fd8329433ce5c1574572cd59c
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>