[POWERPC] 83xx: Update mpc8349emitx(gp) defconfig for USB

USB support for the 8349itx got added a while back; but the defconfig
never got updated.  This patch adds the appropriate USB config options
to the defconfigs

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
CC: Scott Wood <scottwood@freescale.com>
CC: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>