mfd: sec: Fix reg_offset for interrupt registers

reg_offset is offset of the status/mask registers. Now, since status_base
and mask_base are pointing to corresponding first registers, reg_offset
should start from 0 otheriwse regmap_add_irq_chip will fail during probe.

Signed-off-by: Inderpal Singh <inderpal.singh@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>