drm/sched: Remove weak paused submission checks

There is no need to check the boolean in the work item's prologues since
the boolean can be set at any later time anyway.

The helper which pauses submission sets it and synchronously cancels the
work and helpers which queue the work check for the flag so all should be
good.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Danilo Krummrich <dakr@redhat.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Philipp Stanner <pstanner@redhat.com>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250114105942.64832-1-tvrtko.ursulin@igalia.com