clk: renesas: r8a7795: Correct lvds clock parent

According to the latest information, the parent clock of the LVDS module
clock is the S0D4 clock, not the S2D1 clock.

Note that this change has no influence on actual operation, as the
rcar-du LVDS encoder driver doesn't use the parent clock's rate.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>