regmap: irq: Enable irq retriggering for nested irqs

When nested interrupts are handled with regmap irq framework, we need to
mark the interrupts to be resend for pending interrupts on enable_irq.
Else the events might be lost for nested irqs.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Tested-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>