clk: shmobile: r8a7795: Add SD divider support

This patch adds SD[0..3] clock divider support for R-Car Gen3 SoC.

Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>