pinctrl: sh-pfc: r8a7791/r8a7793: Correct SCIFB1_B SCK MOD_SEL value

When using serial port SCIFB1_B, transmit works, but nothing is
received.

Receive fails because the SCIFB1_SCK_B settings configure the wrong
value for the sel_scifb1 field in the Module Select Register (MOD_SEL),
due to an ambiguity in the R-Car M2-W and M2-N datasheets.

Tested on r8a7791/koelsch using pins 53 (TXD) and 72 (RXD) on EXIO
Connector A.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Linus Walleij <linus.walleij@linaro.org>