sh: LCDC SYS bus access wait fix

Update the SuperH Mobile LCDC driver to wait for SYS bus to
become idle after reading or writing. This is needed by the
kfr2r09 board, but also fixes potential problems on other
boards making use of the LCDC in a SYS configuration.

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