powerpc/82xx: updates for mgcoge

Add:
 - Setup dts node for USB
 - pin description and setup for SMC1 (serial interface)

Update and cleanup mgcoge_defconfig:
- enable: TIPC, UBIFS, USB_GADGET driver, SQUASHFS, HIGHRES timers
          POSIX_MQUEUE, EMBEDDED
- disable: EXT3, PPC_PMAC

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Acked-by: Heiko Schocher <hs@denx.de>
cc: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>