[media] media: venus: hfi_venus: fix variable dereferenced before check

This fixes a warning found when building with gcc7:

drivers/media/platform/qcom/venus/hfi_venus.c:998
venus_isr_thread() warn: variable dereferenced before check
'hdev' (see line 994)

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

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

@@ -991,13 +991,14 @@ static void venus_process_msg_sys_error(struct venus_hfi_device *hdev,
 static irqreturn_t venus_isr_thread(struct venus_core *core)
 {
 	struct venus_hfi_device *hdev = to_hfi_priv(core);
-	const struct venus_resources *res = hdev->core->res;
+	const struct venus_resources *res;
 	void *pkt;
 	u32 msg_ret;
 
 	if (!hdev)
 		return IRQ_NONE;
 
+	res = hdev->core->res;
 	pkt = hdev->pkt_buf;
 
 	if (hdev->irq_status & WRAPPER_INTR_STATUS_A2HWD_MASK) {