mfd: palmas: Add rtc irq number as irq resource for palmas-rtc

Palma RTC is capable of generating alarm interrupt. Pass the alarm interrupt
as IRQ_RESOURCE for palmas-rtc sub device driver so that rtc driver can get
irq as platform_get_irq().

Also pass the irq domain in mfd_add_devices() to properly offset the irqs for
sub devices. This is needed when adding device through DT.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>