gbm: do not export _gbm_mesa_get_device

This symbol is internal and was never part of the API.
Unused by any of the gbm backends, it makes sense to
simply not export it.

Cc: Kristian Høgsberg <krh@bitplanet.net>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>

src/gbm/main/gbm.c

@@ -100,7 +100,7 @@ gbm_device_destroy(struct gbm_device *gbm)
       gbm->destroy(gbm);
 }
 
-GBM_EXPORT struct gbm_device *
+struct gbm_device *
 _gbm_mesa_get_device(int fd)
 {
    struct gbm_device *gbm = NULL;

src/gbm/main/gbmint.h

@@ -110,7 +110,7 @@ struct gbm_backend {
    struct gbm_device *(*create_device)(int fd);
 };
 
-GBM_EXPORT struct gbm_device *
+struct gbm_device *
 _gbm_mesa_get_device(int fd);
 
 #endif