mfd: ab8500-debug: Print banks in hex

This patch changes bank prints to use hex value.

Signed-off-by: Mattias Wallin <mattias.wallin@stericsson.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Marcus COOPER <marcus.xm.cooper@stericsson.com>
Reviewed-by: Daniel WILLERUD <daniel.willerud@stericsson.com>
Tested-by: Jonas ABERG <jonas.aberg@stericsson.com>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>