powerpc/82xx: rename and update mgcoge board support
The mgcoge board from keymile is now base for some other
similar boards. Therefore the board specific name mgcoge
was renamed to a generic name km82xx. Additionally some
enhancements were made:
- rework partition table in dts file
- add cpm2_pio_c gpio controller in dts file
- update defconfig
- add pin description for SCC1
- add pin description and configuration for USB
Signed-off-by: Holger Brunck <holger.brunck@keymile.com> Acked-by: Heiko Schocher <hs@denx.de> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org> CC: Heiko Schocher <hs@denx.de> Signed-off-by: Kumar Gala <galak@kernel.crashing.org>