sh: intc: Confine SH_INTC to platforms that need it

Currently the sh-intc driver is compiled on all SuperH and
non-multiplatform SH-Mobile platforms, while it's only used on a limited
number of platforms:
  - SuperH: SH2(A), SH3(A), SH4(A)(L) (all but SH5)
  - ARM: sh7372, sh73a0

Drop the "default y" on SH_INTC, make all CPU platforms that use it
select it, and protect all sub-options by "if SH_INTC" to fix this.

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