drm/msm: change msm_sched_ops from global to static

Smatch reports this issue
msm_ringbuffer.c:43:36: warning: symbol 'msm_sched_ops' was not declared. Should it be static?

msm_sched_ops is only used in msm_ringbuffer.c so change its
storage-class specifier to static.

Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/482883/
Link: https://lore.kernel.org/r/20220421131507.1557667-1-trix@redhat.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>