sh: add a start_transfer() callback to the LCDC driver

This patch adds a ->start_transfer() callback to the
driver sh_mobile_lcdcfb.c. The callback is used to
program the LCDC panel in the case of one-shot mode.

Needed by the LCD controller used on the KFR2R09 board.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>