drm/radeon: add userptr config option

This allows selecting CONFIG_MMU_NOTIFIER if it isn't already selected.
Signed-off-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/Kconfig

+config DRM_RADEON_USERPTR
+	bool "Always enable userptr support"
+	depends on DRM_RADEON
+	select MMU_NOTIFIER
+	help
+	  This option selects CONFIG_MMU_NOTIFIER if it isn't already
+	  selected to enabled full userptr support.
+
 config DRM_RADEON_UMS
 	bool "Enable userspace modesetting on radeon (DEPRECATED)"
 	depends on DRM_RADEON