sh: Add Renesas EDOSK7760 board support.

This adds support for the Renesas (RTE) EDOSK7760 board. Currently
supported devices are:

	 - ramdisk support
	 - ethernet support
	 - nfs support
	 - ext2/ext3 support
	 - i2c support
	 - fb support (M)

Signed-off-by: Luca Santini <luca.santini@spesonline.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>