sh-pfc: r8a7791: Fix DU pin groups organisation

Rename the sync_1 group to sync as the device has a single sync pin
group for the DU, move the cde_disp mux array right after the
corresponding pins array, and split the clk_in pins in three separate
groups as the pins can be used independently.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>