drm/amdkfd: Fix NULL pointer dereference

Check that adev->gfx.ras is valid before using it.

Fixes: 6475ae2b742876 ("drm/amdgpu: add UTCL2 RAS poison query for Aldebaran (v2)")
CC: Tao Zhou <[e-mail]>
Signed-off-by: Felix Kuehling <[e-mail]>
Reviewed-by: Mukul Joshi <[e-mail]>
Reviewed-by: Hawking Zhang <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

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

···
 
 bool amdgpu_amdkfd_ras_query_utcl2_poison_status(struct amdgpu_device *adev)
 {
-	if (adev->gfx.ras->query_utcl2_poison_status)
+	if (adev->gfx.ras && adev->gfx.ras->query_utcl2_poison_status)
 		return adev->gfx.ras->query_utcl2_poison_status(adev);
 	else
 		return false;