ARM: OMAP1: Change interrupt numbering for sparse IRQ

Change interrupt numbering for sparse IRQ. We do this using
a fixed offset until we can drop irqs.h once all it's users
have been updated.

Note that this depends on the GPIO fix for the MPUIO IRQs
"gpio: omap: Fix regression for MPUIO interrupts".

Also note that this patch adds some extra irq alloc warnings
that will go away when we stop calling irq_alloc_descs
in gpio-omap.c with a follow-up patch.

Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Tony Lindgren <tony@atomide.com>