commands: usbgadget: provide fallback to global variables ...

usbgadget autostarter is providing now a global variable to configure fastboot.
We can use is as fallback for the cmd_usbgadget as well.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

usb: gadget: properly release f_multi_opts ...

The usbgadget commands uses statically allocated f_multi_opts and passes
this to usb_multi_register(). These f_multi_opts are of course no
longer valid when we leave the usbgadget command. Luckily we do not use
the data after we left the usbgadget command, so this never has been a
problem. However, f_multi_opts has some allocated members which we can
not free anymore on gadget unregistration because we no longer have the
pointer to them.

Fix this by adding a release function to struct f_multi_opts. This way
we can allocate all memory dynamically and properly free it when not
used anymore.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

commands: usbgadget: Fix -d option help text ...

The -d option disables any currently active gadget, it does not
necessarily have to be a serial gadget.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

USB: gadget: Add a multi function gadget ...

Similar to the Kernel multi function this gadget driver is used
for creating a USB device with multiple functions. This is
created and removed with the newly created 'usbgadget' command.
Based on the options it creates combinations of DFU, fastboot
and serial USB functions.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>