mx53loco: Add mc34708 support and set mx53 frequency at 1GHz

Add mc34708 support and set mx53 core frequency at its maximum value of 1GHz.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Jason Liu <r64343@freescale.com>
Acked-by: Stefano Babic <sbabic@denx.de>