irqchip/renesas-rzg2l: Drop redundant IRQC_TINT_START check in rzg2l_irqc_alloc()

irqchip/renesas-rzg2l: Drop redundant IRQC_TINT_START check in rzg2l_irqc_alloc()

The check `hwirq < IRQC_TINT_START` in rzg2l_irqc_alloc() is unnecessary as
the condition is already guaranteed to be false at that point in the code.

The outer `if (hwirq > IRQC_IRQ_COUNT)` block ensures that hwirq is always
above IRQC_IRQ_COUNT before reaching this check, and since IRQC_TINT_START
<= IRQC_IRQ_COUNT, the guard can never trigger.

Remove the dead code to simplify the allocation path.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260325192451.172562-5-biju.das.jz@bp.renesas.com