drm/msm/sde: always populate the fence-fd in sde fence create

Fix the sde_fence_create api to always set the
fence-fd, which is passed as an argument. Currently,
in the path where it identifies, the FD already exists
for the fence, fd is missed to be set, which leads to
invalid fd being passed to user-mode.

Change-Id: Ic841ad32264f31900f347aced0ad140cceb27565
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>