clk: renesas: r8a7795: Add IIC-DVFS clock

This patch adds DVFS clock for R8A7795 SoC.

Signed-off-by: Keita Kobayashi <keita.kobayashi.ym@renesas.com>
Signed-off-by: Gaku Inami <gaku.inami.xw@bp.renesas.com>
Signed-off-by: Dien Pham <dien.pham.ry@rvc.renesas.com>
Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>