of/irq: Refer to actual buffer size in of_irq_parse_one()

of/irq: Refer to actual buffer size in of_irq_parse_one()

Replace two open-coded calculations of the buffer size by invocations of
sizeof() on the buffer itself, to make sure the code will always use the
actual buffer size.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/817c0b9626fd30790fc488c472a3398324cfcc0c.1724156125.git.geert+renesas@glider.be
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>