ARM: mach-shmobile: Add support for PINT though INTC macros

Add a INTC_PINT() macro with various helper bits to allow SoCs
like sh73a0 to suppor the PINT hardware using regular INTC tables.

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