mfd: max8925: Add irqdomain for dt

Add irqdomains for max8925's main irq, wrap irq register operations
into irqdomain's map func. it is necessary for dt support.

Also, add dt support for max8925 driver.

Signed-off-by: Qing Xu <qingx@marvell.com>
Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>