Add a common stub config for shinano

* Add stubs CONFIG_MACH_SHINANO,
  selected if any of their devices are selected.
* Much cleaner ifdefs in {clock,board}-8974.c now.

Change-Id: I315a9599c8430da18a70ac2154798e5f30089525

Conflicts:
	arch/arm/mach-msm/Kconfig