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: NKim Phillips <kim.phillips@freescale.com>
Signed-off-by: NTimur Tabi <timur@freescale.com>
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>