usb: typec: mux: Introduce GPIO-based SBU mux

A design found in various Qualcomm-based boards is to use a USB switch,
controlled through a pair of GPIO lines to connect, disconnect and
switch the orientation of the SBU lines in USB Type-C applications.

This introduces a generic driver, which implements the typec_switch and
typec_mux interfaces to perform these operations.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>