The patch fixes these compiler's warnings:

  lib/gui/bmp.c:12:15: warning: no previous prototype for 'bmp_open' [-Wmissing-prototypes]
   struct image *bmp_open(char *inbuf, int insize)
                 ^
  lib/gui/bmp.c:33:6: warning: no previous prototype for 'bmp_close' [-Wmissing-prototypes]
   void bmp_close(struct image *img)
        ^

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>