media: venus: vdec: Fix forgotten mutex unlock in start streaming

This fixes the following smatch warning in the error path:

drivers/media/platform/qcom/venus/vdec.c:968 vdec_start_streaming()
 warn: inconsistent returns 'mutex:&inst->lock'.
  Locked on:   line 952
  Unlocked on: line 963
               line 968

by goto mutex unlock.
Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/platform/qcom/venus/vdec.c

@@ -949,7 +949,7 @@ static int vdec_start_streaming(struct vb2_queue *q, unsigned int count)
 
 	ret = venus_pm_acquire_core(inst);
 	if (ret)
-		return ret;
+		goto error;
 
 	if (q->type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE)
 		ret = vdec_start_capture(inst);