egl-fbdev: Fix compile-error by including errno.h

We use errno and EINVAL so include errno.h.

This patch introduced this bug:
http://cgit.freedesktop.org/mesa/mesa/commit/src/gallium/state_trackers/egl/fbdev/native_fbdev.c?id=b60120608f6ddf4098bc324363197c979ee04cb7

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Cc: Chia-I Wu <olv@lunarg.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Adam Jackson <ajax@redhat.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>

src/gallium/state_trackers/egl/fbdev/native_fbdev.c

@@ -41,6 +41,7 @@
  *  - no pixmap support
  */
 
+#include <errno.h>
 #include <sys/ioctl.h>
 #include <sys/types.h>
 #include <sys/stat.h>