sh: intc - irl mode update for sh7780 and sh7785

This patch contains the following fixes and improvements:
- Fix address typo for INTMSK2 / INTMSKCLR2 registers on sh7780.
- Adds IRQ_MODE_IRLnnnn_MASK using intc controller for IRL masking.
- Good old IRQ_MODE_IRLnnnn should not register any intc controller.
- plat_irq_setup_pins() now selects IRL or IRQ mode.
- the holding function is now disabled using ICR0.

By default all external pin interrupts are disabled.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>