drm/i915: Lock timeline mutex directly in error path of eb_pin_timeline

Don't use the interruptable version of the timeline mutex lock in the
error path of eb_pin_timeline as the cleanup must always happen.

v2:
 (John Harrison)
  - Don't check for interrupt during mutex lock
v3:
 (Tvrtko)
  - A comment explaining why lock helper isn't used

Fixes: 544460c3 ("drm/i915: Multi-BB execbuf")
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220111163929.14017-1-matthew.brost@intel.com

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

@@ -2497,9 +2497,14 @@ static int eb_pin_timeline(struct i915_execbuffer *eb, struct intel_context *ce,
 				      timeout) < 0) {
 			i915_request_put(rq);
 
-			tl = intel_context_timeline_lock(ce);
+			/*
+			 * Error path, cannot use intel_context_timeline_lock as
+			 * that is user interruptable and this clean up step
+			 * must be done.
+			 */
+			mutex_lock(&ce->timeline->mutex);
 			intel_context_exit(ce);
-			intel_context_timeline_unlock(tl);
+			mutex_unlock(&ce->timeline->mutex);
 
 			if (nonblock)
 				return -EWOULDBLOCK;