SCIF0 on R-Car E2 does not have an SCK pin.

"SCIF_CLK" is the (H)SCIF baud rate generation clock pin, which is not
yet supported.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Linus Walleij <linus.walleij@linaro.org>