GCC4.6: Squash warning in mpc5121ads.c

mpc5121ads.c: In function 'misc_init_r':
mpc5121ads.c:256: warning: format '%02lx' expects type 'long unsigned int', but
argument 2 has type 'int'
mpc5121ads.c:263: warning: format '%02lx' expects type 'long unsigned int', but
argument 2 has type 'int'

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Mike Frysinger <vapier@gentoo.org>