mfd: Bulk conversion to generic_handle_domain_irq()

Wherever possible, replace constructs that match either
generic_handle_irq(irq_find_mapping()) or
generic_handle_irq(irq_linear_revmap()) to a single call to
generic_handle_domain_irq().

Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>