[POWERPC] 83xx: Add support for MPC8349E-mITX-GP

This patch adds a defconfig and a DTS for the MPC8349E-mITX-GP, a variant of
the MPC8349E-mITX.

USB is disabled because the only USB port is not setup properly by
firmware/kernel

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>