[media] s5p-mfc: Fix clock management in s5p_mfc_release() function

Clock control indirectly requires access to MFC device, so call it only
if we are sure that the device exists in s5p_mfc_release function.
s5p_mfc_remove() calls s5p_mfc_final_pm(), which releases all PM related
resources, including clocks, so any call to clocks related functions
is not valid after s5p_mfc_final_pm().

Fixes: d695c12c ("[media] media: s5p-mfc fix invalid memory access from
s5p_mfc_release()")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/s5p-mfc/s5p_mfc.c

@@ -929,10 +929,11 @@ static int s5p_mfc_release(struct file *file)
 	mfc_debug_enter();
 	if (dev)
 		mutex_lock(&dev->mfc_mutex);
-	s5p_mfc_clock_on();
 	vb2_queue_release(&ctx->vq_src);
 	vb2_queue_release(&ctx->vq_dst);
 	if (dev) {
+		s5p_mfc_clock_on();
+
 		/* Mark context as idle */
 		clear_work_bit_irqsave(ctx);
 		/*
@@ -954,9 +955,9 @@ static int s5p_mfc_release(struct file *file)
 			if (s5p_mfc_power_off() < 0)
 				mfc_err("Power off failed\n");
 		}
-	}
 		mfc_debug(2, "Shutting down clock\n");
 		s5p_mfc_clock_off();
+	}
 	if (dev)
 		dev->ctx[ctx->num] = NULL;
 	s5p_mfc_dec_ctrls_delete(ctx);