irqchip/renesas-rzv2h: Clarify IRQ range definitions and tighten TINT validation

irqchip/renesas-rzv2h: Clarify IRQ range definitions and tighten TINT validation

Introduce ICU_IRQ_LAST and ICU_TINT_LAST macros to make range boundaries
explicit and reduce the chance of off-by-one errors.

Extract the TINT information up front in rzv2h_icu_alloc() and validate
the resulting hardware IRQ against the full TINT range
[ICU_TINT_START, ICU_TINT_LAST].

[ tglx: Convert the hard to parse inverse conditions to use a simple helper
  	macro hwirq_within() which is easy to read, less error prone and
  	avoids a lot of typing ]

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260304113317.129339-5-prabhakar.mahadev-lad.rj@bp.renesas.com