mfd: ab8500-debugfs: Dump sim registers

This patch allows to dump the SIM registers from debugfs. It will
temporary change the config to allow APE side to read the SIM registers.
Note that this read can cause problem on modem side since the modem
can't read these registers while the operation is ongoing.

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: Jonas ABERG <jonas.aberg@stericsson.com>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>