Always enable userptr support

configname: CONFIG_DRM_RADEON_USERPTR

Linux Kernel Configuration
└─>Device Drivers
└─>Graphics support
└─>Direct Rendering Manager
└─>Always enable userptr support
In linux kernel since version 3.10 (release Date: 2013-06-30)  
This option selects CONFIG_MMU_NOTIFIER if it isn't already
selected to enabled full userptr support.