RZ/G2L interrupt chips require that the interrupt is masked before changing
the NMI, IRQ, TINT interrupt settings. Aside of that, after setting an edge
trigger type it is required to clear the interrupt status register in order
to avoid spurious interrupts.

The current implementation fails to do either of that and therefore is
prone to generate spurious interrupts when setting the trigger type.

Address this by:

  - Ensuring that the interrupt is masked at the chip level across the
    update for the TINT chip

  - Clearing the interrupt status register after updating the trigger mode
    for edge type interrupts

[ tglx: Massaged changelog and reverted the spin_lock_irqsave() change as
  	the set_type() callback is always called with interrupts disabled. ]

Fixes: 3fed0955 ("irqchip: Add RZ/G2L IA55 Interrupt Controller driver")
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>