media: venus: venc: Fix potential null pointer dereference on pointer fmt

Currently the call to find_format can potentially return a NULL to
fmt and the nullpointer is later dereferenced on the assignment of
pixmp->num_planes = fmt->num_planes.  Fix this by adding a NULL pointer
check and returning NULL for the failure case.

Addresses-Coverity: ("Dereference null return")

Fixes: aaaa93eda6 ("[media] media: venus: venc: add video encoder files")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

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

@@ -183,6 +183,8 @@ venc_try_fmt_common(struct venus_inst *inst, struct v4l2_format *f)
 		else
 			return NULL;
 		fmt = find_format(inst, pixmp->pixelformat, f->type);
+		if (!fmt)
+			return NULL;
 	}
 
 	pixmp->width = clamp(pixmp->width, frame_width_min(inst),