The mux clk type within the MediaTek clk driver library only has a
register function, and no corresponding unregister function. This
means there is no way for its users to properly implement cleanup
and removal.
Add a matching unregister function for the mux type clk.
Signed-off-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>
Reviewed-by: Miles Chen <miles.chen@xxxxxxxxxxxx>