drm/lima: Make lima_sched_ops static

Fix sparse warning:

drivers/gpu/drm/lima/lima_sched.c:356:36: warning:
 symbol 'lima_sched_ops' was not declared. Should it be static?

Fixes: a1d2a633 ("drm/lima: driver for ARM Mali4xx GPUs")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Qiang Yu <yuq825@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190416144353.34024-1-yuehaibing@huawei.com