gbm: Removed unused function.

AFAICT, it's never been used.

It was briefly nudged in the right direction here:
commit 10e5ffd496
Author: Emil Velikov <emil.l.velikov@gmail.com>
Date:   Sat Jan 25 17:19:10 2014 +0000

    gbm: do not export _gbm_mesa_get_device

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Kristian H. Kristensen <hoegsberg@chromium.org>

src/gbm/main/gbm.c

@@ -104,32 +104,6 @@ gbm_device_destroy(struct gbm_device *gbm)
       gbm->destroy(gbm);
 }
 
-struct gbm_device *
-_gbm_mesa_get_device(int fd)
-{
-   struct gbm_device *gbm = NULL;
-   struct stat buf;
-   dev_t dev;
-   int i;
-
-   if (fd < 0 || fstat(fd, &buf) < 0 || !S_ISCHR(buf.st_mode)) {
-      errno = EINVAL;
-      return NULL;
-   }
-
-   for (i = 0; i < device_num; ++i) {
-      dev = devices[i]->stat.st_rdev;
-      if (major(dev) == major(buf.st_rdev) &&
-          minor(dev) == minor(buf.st_rdev)) {
-         gbm = devices[i];
-         gbm->refcount++;
-         break;
-      }
-   }
-
-   return gbm;
-}
-
 /** Create a gbm device for allocating buffers
  *
  * The file descriptor passed in is used by the backend to communicate with

src/gbm/main/gbmint.h

@@ -117,7 +117,4 @@ struct gbm_backend {
    struct gbm_device *(*create_device)(int fd);
 };
 
-struct gbm_device *
-_gbm_mesa_get_device(int fd);
-
 #endif