clk: mediatek: mux: Update parent at enable time

The mux clocks don't always correctly take the new parent into account
when the parent is updated while the clock is disabled. Set the update
bit when enabling the clock to force an update of the mux.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/20210125170819.26130-3-laurent.pinchart@ideasonboard.com


Reviewed-by: Weiyi Lu <weiyi.lu@mediatek.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>