drm/amdgpu: use designated initialiser for thermal_irq_src.

This fixes the 0-day build warning.
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/amd/powerplay/hwmgr/hwmgr.c

@@ -124,9 +124,9 @@ static int phm_ctf_irq(void *private_data,
 }
 
 static const struct cgs_irq_src_funcs thermal_irq_src[3] = {
-	{NULL, phm_thermal_l2h_irq},
-	{NULL, phm_thermal_h2l_irq},
-	{NULL, phm_ctf_irq}
+	{ .handler = phm_thermal_l2h_irq },
+	{ .handler = phm_thermal_h2l_irq },
+	{ .handler = phm_ctf_irq }
 };
 
 int hwmgr_early_init(struct pp_instance *handle)