media: amphion: fix REVERSE_INULL issues reported by coverity

null-checking of a pointor is suggested before dereferencing it

Fixes: 9f599f35 ("media: amphion: add vpu core driver")
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Ming Qian <ming.qian@nxp.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

drivers/media/platform/amphion/venc.c

@@ -268,7 +268,7 @@ static int venc_g_parm(struct file *file, void *fh, struct v4l2_streamparm *parm
 {
 	struct vpu_inst *inst = to_inst(file);
 	struct venc_t *venc = inst->priv;
-	struct v4l2_fract *timeperframe = &parm->parm.capture.timeperframe;
+	struct v4l2_fract *timeperframe;
 
 	if (!parm)
 		return -EINVAL;
@@ -279,6 +279,7 @@ static int venc_g_parm(struct file *file, void *fh, struct v4l2_streamparm *parm
 	if (!vpu_helper_check_type(inst, parm->type))
 		return -EINVAL;
 
+	timeperframe = &parm->parm.capture.timeperframe;
 	parm->parm.capture.capability = V4L2_CAP_TIMEPERFRAME;
 	parm->parm.capture.readbuffers = 0;
 	timeperframe->numerator = venc->params.frame_rate.numerator;
@@ -291,7 +292,7 @@ static int venc_s_parm(struct file *file, void *fh, struct v4l2_streamparm *parm
 {
 	struct vpu_inst *inst = to_inst(file);
 	struct venc_t *venc = inst->priv;
-	struct v4l2_fract *timeperframe = &parm->parm.capture.timeperframe;
+	struct v4l2_fract *timeperframe;
 	unsigned long n, d;
 
 	if (!parm)
@@ -303,6 +304,7 @@ static int venc_s_parm(struct file *file, void *fh, struct v4l2_streamparm *parm
 	if (!vpu_helper_check_type(inst, parm->type))
 		return -EINVAL;
 
+	timeperframe = &parm->parm.capture.timeperframe;
 	if (!timeperframe->numerator)
 		timeperframe->numerator = venc->params.frame_rate.numerator;
 	if (!timeperframe->denominator)