drm/amdgpu/irq: check if nbio funcs exist

We need to check if the nbios funcs exist before
checking the individual pointers.

Signed-off-by: Alex Deucher <[e-mail]>
Reviewed-by: Hawking Zhang <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c

···
 	 * register to check whether the interrupt is triggered or not, and properly
 	 * ack the interrupt if it is there
 	 */
-	if (adev->nbio.funcs->handle_ras_controller_intr_no_bifring)
+	if (adev->nbio.funcs &&
+	    adev->nbio.funcs->handle_ras_controller_intr_no_bifring)
 		adev->nbio.funcs->handle_ras_controller_intr_no_bifring(adev);
 
-	if (adev->nbio.funcs->handle_ras_err_event_athub_intr_no_bifring)
+	if (adev->nbio.funcs &&
+	    adev->nbio.funcs->handle_ras_err_event_athub_intr_no_bifring)
 		adev->nbio.funcs->handle_ras_err_event_athub_intr_no_bifring(adev);
 
 	return ret;