msm: kgsl: Correct the fence reference counting

The sync_file_create() function takes an additional refcount to the
fence. Update the refcounting to avoid a memory leak.

Change-Id: I684377e5a27a2c318fc6f26d0e6ba4a21da1cf9f
Signed-off-by: Lynus Vaz <lvaz@codeaurora.org>