clk: nuvoton: Use clk_parent_data instead of string for parent clock

For the declaration of parent clocks, use struct clk_parent_data instead
of a string. Due to the change in the passed arguments, replace the usage
of devm_clk_hw_register_mux() with clk_hw_register_mux_parent_data() for
all cases.
Signed-off-by: Jacky Huang <ychuang3@nuvoton.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>