irqchip/renesas-rzv2h: Prevent TINT spurious interrupt

A spurious TINT interrupt is seen during boot on RZ/G3E SMARC EVK.

A glitch in the edge detection circuit can cause a spurious interrupt.

Clear the status flag after setting the ICU_TSSRk registers, which is
recommended in the hardware manual as a countermeasure.

Fixes: 0d7605e7 ("irqchip: Add RZ/V2H(P) Interrupt Control Unit (ICU) driver")
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org