gbm: use the loader util lib

gbm: use the loader util lib

Additionally this commit removes the following exported functions

   _gbm_udev_device_new_from_fd()
   _gbm_fd_get_device_name()
   _gbm_log()

All three were erroneously marked as exported since their inception.
Neither of them has ever been a part of the API thus there should be
no users of them.

Cc: Chad Versace <chad.versace@linux.intel.com>
Cc: Kristian Høgsberg <krh@bitplanet.net>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>