ARM: mach-shmobile: Use common INTC IRQ code on sh73a0

Improve IRQ triggering support by making use of the macro
INTC_IRQ_PINS_32() for INTCA on sh73a0. Unfortunately it
is not as easy as just using the macro as-is, we need to
do mask and unmaks in the GIC but configure other bits
and ack in INTCA. Update GPIO IRQ mappings while at it.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>