mfd: tps65910: Use regmap irq framework for interrupt support

Implement irq support of tps65910 with regmap irq framework
in place of implementing locally.
This reduces the code size significantly and easy to maintain.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>