clk: renesas: Allow compile-testing of all (sub)drivers

Enable compile-testing of the remaining clock drivers and subdrivers,
now dummies are available for of_clk_get_from_provider(),
of_device_compatible_match(), and rcar_rst_read_mode_pins(), and the
CPG/MSSR driver core has been converted from of_match_node() to
of_device_get_match_data().

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>