i.MX51: add support for cpuimx51 module and its baseboard

CPUIMX51 is build around Freescale's i.MX515 and has up to
512MB of RAM, NAND Flash, Ethernet, USB Host with 4 ports
hub, USB OTG, ST16554 Quad UART on nCS1, I2C RTC ...

MBIMX51 adds LEDS, Keypad, TSC2007 touchscreen controler ...

Signed-off-by: Eric Bénard <eric@eukrea.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>