mfd: palmas: Provide irq flags through DT/platform data

Currently driver sets the irq type to IRQF_TRIGGER_LOW which is
causing interrupt registration failure in ARM based SoCs as:
[    0.208479] genirq: Setting trigger mode 8 for irq 118 failed (gic_set_type+0x0/0xf0)
[    0.208513] dummy 0-0059: Failed to request IRQ 118: -22

Provide the irq flags through platform data if device is registered
through board file or get the irq type from DT node property in place
of hardcoding the irq flag in driver to support multiple platforms.

Also configure the device to generate the interrupt signal according to
flag type.

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