pinctrl: sh-pfc: r8a7796: Add HSCIF pins, groups, and functions

Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
[geert: Fix hscif2_clk_[bc]_mux[] and hscif4_ctrl_mux[]]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>