mxc: Add support for the Babbage board (i.MX5)

Babbage is a reference board from Freescale for their i.MX51 SoC.

Add board definition, Kconfig and Makefiles to enable Freescale i.MX51
processor and Babbage board.

Boot tested on a Babbage2.5 board

Signed-off-by: Amit Kucheria <amit.kucheria@canonical.com>