drm/i915/guc: Check if expecting reply before decrementing outstanding_submission_g2h

When sending a H2G message where a reply is expected in
guc_submission_send_busy_loop(), outstanding_submission_g2h is
incremented before the send. However, if there is an error sending the
message, outstanding_submission_g2h is decremented without checking if a
reply is expected.

Therefore, check if reply is expected when there is a failure before
decrementing outstanding_submission_g2h.

Fixes: 2f2cc53 ("drm/i915/guc: Close deregister-context race against CT-loss")
Signed-off-by: Jesus Narvaez <jesus.narvaez@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Cc: Mousumi Jana <mousumi.jana@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://lore.kernel.org/r/20250514225224.4142684-1-jesus.narvaez@intel.com

Author: jnar17

drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c

@@ -633,7 +633,7 @@ static int guc_submission_send_busy_loop(struct intel_guc *guc,
 		atomic_inc(&guc->outstanding_submission_g2h);
 
 	ret = intel_guc_send_busy_loop(guc, action, len, g2h_len_dw, loop);
-	if (ret)
+	if (ret && g2h_len_dw)
 		atomic_dec(&guc->outstanding_submission_g2h);
 
 	return ret;