mux: add support for delay after muxing

Hardware may require some time for the muxed analog signals to settle
after the muxing is changed.  Allow users of the mux subsystem to
specify this delay with the new mux_control_select_delay() function (and
the _try equivalent).

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Tested-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Peter Rosin <peda@axentia.se>
Link: https://lore.kernel.org/r/20211007134641.13417-2-vincent.whitchurch@axis.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>