pinctrl: sh-pfc: r8a77990: Add Audio clock pins, groups and functions

This patch adds AUDIO_CLK{A,B,C}, AUDIO_CLKOUT, AUDIO_CLKOUT{1,2,3}
pins, groups and functions to the R8A77990 SoC.

Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
[simon: rebase]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>