ARM: mach-shmobile: Run-time IRQ handler for INTCA

Break-out INTC specific IRQ demux code from the file
entry-macro-intc.S and register during run-time.

Covers sh7367, sh7377 and sh7372.

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