drm/amdgpu: Fix compile warning

In function ‘gfx_v9_0_check_fw_write_wait’:
warning: enumeration value ‘CHIP_TAHITI’ not handled in switch [-Wswitch]

Always add default case in case there is no match
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c

@@ -532,6 +532,8 @@ static void gfx_v9_0_check_fw_write_wait(struct amdgpu_device *adev)
 		    (adev->gfx.mec_feature_version >= 42))
 			adev->gfx.mec_fw_write_wait = true;
 		break;
+	default:
+		break;
 	}
 }