drm/msm: Move submit bo flags update from obj lock

The flags are only accessed (1) when submit is constructed, before
enqueuing to gpu sched (ie. when still visible to only the task calling
the submit ioctl), (2) here, where we own a reference to the submit and
are serialized on the gpu sched thread, and (3) after the submit is
retired and last reference is dropped, which is serialized on the
submit's reference count.  Hence locking is unneeded here.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Patchwork: https://patchwork.freedesktop.org/patch/527830/
Link: https://lore.kernel.org/r/20230320144356.803762-3-robdclark@gmail.com