mfd: twl6030-irq: Convert to use linear irq_domain

Since the TWL6030 PMIC is used with OMAP4 SoCs only and OMAP4 legacy
boot is dropped there are no needs to allocate the range of IRQ
descriptors during system boot to support TWL6030 IRQs.

Hence, convert it to use linear irq_domain and move IRQ configuration in
.map()/.unmap() callbacks of irq_domain. So, IRQ mapping and descriptors
allocation will be performed dynamically basing on DT configuration.

The error message will be reported in case if unmapped IRQ is received by
TWL6030 (virq==0).

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Graeme Gregory <gg@slimlogic.co.uk>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>