drm/amdgpu: Fix null pointer dereference

amdgpu_reg_state_sysfs_fini could be invoked at the
time when asic_func is even not initialized, i.e.,
amdgpu_discovery_init fails for some reason.

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

drivers/gpu/drm/amd/include/amdgpu_reg_state.h

···
 }
 
 #define amdgpu_asic_get_reg_state_supported(adev) \
-	((adev)->asic_funcs->get_reg_state ? 1 : 0)
+	(((adev)->asic_funcs && (adev)->asic_funcs->get_reg_state) ? 1 : 0)
 
 #define amdgpu_asic_get_reg_state(adev, state, buf, size)                  \
 	((adev)->asic_funcs->get_reg_state ?                               \