common/board_f: fix gcc warning on MIPS64

This fixes following warning when compiled with MIPS64

common/board_f.c: In function 'display_text_info':
common/board_f.c:150:2: warning: format '%X' expects argument i
  of type 'unsigned int', but argument 2 has type 'long unsigned int' [-Wformat=]
  debug("U-Boot code: %08X -> %08lX  BSS: -> %08lX\n",

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>