Adapt board configuration and fix kernel crash on MCC200 board.

The update procedure was modified to turn off the USB subsystem
before exit for MCC200 and TRAB. This is necessary as otherwise the
USB controller continues to write periodically to system memory!

MCC200-specific notes:
- the patch disables the magic key check for MCC200
- the patch contains the configuration changes made
  for the new revision of the board.

Signed-off-by: Sergei Poselenov <sposelenov@emcraft.com>
Signed-off-by: Wolfgang Denk <wd@denx.de>