gbm: Fix width height getters return type (trivial)

v2: Other way round... to make consistent, make both return type have
the fixed width - uint32_t.

Cc: Daniel Stone <daniel@fooishbar.org>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Acked-by: Daniel Stone <daniels@collabora.com>

src/gbm/main/gbm.c

@@ -137,7 +137,7 @@ gbm_create_device(int fd)
  * \return The width of the allocated buffer object
  *
  */
-GBM_EXPORT unsigned int
+GBM_EXPORT uint32_t
 gbm_bo_get_width(struct gbm_bo *bo)
 {
    return bo->width;
@@ -148,7 +148,7 @@ gbm_bo_get_width(struct gbm_bo *bo)
  * \param bo The buffer object
  * \return The height of the allocated buffer object
  */
-GBM_EXPORT unsigned int
+GBM_EXPORT uint32_t
 gbm_bo_get_height(struct gbm_bo *bo)
 {
    return bo->height;