irqchip/renesas-rzg2l: Drop IRQC_IRQ_COUNT macro

irqchip/renesas-rzg2l: Drop IRQC_IRQ_COUNT macro

The total number of external interrupts in RZ/G2L and RZ/G3L SoC are
different. The RZ/G3L has 16 external interrupts whereas RZ/G2L has only 8
external interrupts. Add irq_count variable in struct rzg2l_hw_info to
handle these differences and drop the macro IRQC_IRQ_COUNT.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260325192451.172562-15-biju.das.jz@bp.renesas.com