irqchip/renesas-rzg2l: Add macro to retrieve TITSR register offset based on register...

irqchip/renesas-rzg2l: Add macro to retrieve TITSR register offset based on register's index

[ Upstream commit 2eca4731cc66563b3919d8753dbd74d18c39f662 ]

There are 2 TITSR registers available on the IA55 interrupt controller.

Add a macro that retrieves the TITSR register offset based on it's
index. This macro is useful in when adding suspend/resume support so both
TITSR registers can be accessed in a for loop.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20231120111820.87398-7-claudiu.beznea.uj@bp.renesas.com
Stable-dep-of: 853a6030303f ("irqchip/renesas-rzg2l: Prevent spurious interrupts when setting trigger type")
Signed-off-by: Sasha Levin <sashal@kernel.org>