[POWERPC] Fix kernel build errors for mpc8272ads and mpc8560ads

Recent update of asm-powerpc/io.h caused cpm-related stuff to break in the
current kernel. Current patch fixes it, as well as other inconsistencies
expressed, that do not permit targets from working properly:

- Updated dts with a chosen node with interrupt controller,
- fixed messed device IDs among CPM2 SoC devices,
- corrected odd header name and fixed type in defines,
- Added 82xx subdir to the powerpc/platforms Makefile, missed during
  initial commit,
- new solely-powerpc header file for 8260 family (was using one from
  arch/ppc, this one cleaned up from the extra stuff), in fact for now
  a placeholder to get the board-specific includes for stuff not yet
  capable to live with devicetree peeks only
- Fixed couple of misprints in reference mpc8272 dts.

Signed-off-by: Vitaly Bordug <vbordug@ru.mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>