drm/lima/lima_sched: Remove unused and unnecessary variable 'ret'

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/lima/lima_sched.c: In function ‘lima_sched_run_job’:
 drivers/gpu/drm/lima/lima_sched.c:227:20: warning: variable ‘ret’ set but not used [-Wunused-but-set-variable]

Cc: Qiang Yu <yuq825@gmail.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: dri-devel@lists.freedesktop.org
Cc: lima@lists.freedesktop.org
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Qiang Yu <yuq825@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201113134938.4004947-24-lee.jones@linaro.org