drm/msm/sde: add output fence utility functions

Create shared functions to support Android release and retire
fences in the future. These functions utilize a common sde_fence
structure to generically handle creation and signaling of both
output fence types.

Change-Id: I7d56bd315cc7ab997737f4c684fc95480ace4a3b
Signed-off-by: Clarence Ip <cip@codeaurora.org>