sh: add r8a66597 usb0 host to the se7724 board

Add USB host support for port CN27 on the Solution Engine 7724
board. The r8a66597-hcd driver is hooked up as a platform device
and some registers are configured to enable the USB host function.
The hardware driving the USB port is the on-chip USB0 block in
the sh7724 processor configured as USB host controller.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>