drm/msm: Return ERR_PTR() from submit_create()

In the next patch, we start having more than a single potential failure
reason.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20210728010632.2633470-9-robdclark@gmail.com


Signed-off-by: Rob Clark <robdclark@chromium.org>