sh: sh7785lcr mode pin configuration

This patch adds mode pin support to the sh7785lcr board.

The harware allows the user to control the mode pins using
dip switches S1 and S2, but from the software the pins are
fixed to the factory default since we have no way to reading
out this configuration from software.

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