clk: shmobile: r8a73a4 common clock framework implementation

Driver for the R8A73A4's clocks that are too specific to be supported by a
generic driver.

Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
Acked-by: Michael Turquette <mturquette@linaro.org>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>