pinctrl: sh-pfc: r8a7796: Add CAN FD support

This patch adds CAN FD[0-1] pinmux support to r8a7796 SoC.

Based on a patch for r8a7795 by Ramesh Shanmugasundaram.

Signed-off-by: Chris Paterson <chris.paterson2@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>