mfd: pcf50633: Remove unused platform IRQ code

As part of the pcf50633 removal, take out it's irq code
(which includes one bit still called from the core, but it'll
go soon).

Signed-off-by: "Dr. David Alan Gilbert" <linux@treblig.org>
Link: https://lore.kernel.org/r/20250311014959.743322-9-linux@treblig.org


Signed-off-by: Lee Jones <lee@kernel.org>