ARM: shmobile: Move legacy INTC definitions from irqs.h to intc.h

Move all definitions for legacy INTC from the common "irqs.h" to the
INTC-specific "intc.h".
Include "intc.h" in sh7372/sh73a0 CPU and board files where needed.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Magnus Damm <damm+renesas@opensource.se>
[horms+renesas@verge.net.au: omitted whitespace change]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>