powerpc: add defconfig for Freescale MPC8349E-mITX board

Provide default configuration for the Freescale MPC8349E-mITX board, including
the on-board 16MB flash.

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