Expose more hardware information via ioctls

[xairy]

The Gadget subsystem provides information about the capabilities of the UDC hardware. It might be useful to expose this information via Raw Gadget ioctls.

[xairy]

One of the things we need to expose is usb_gadget->ep0->maxpacket: looks like some UDCs expect bMaxPacketSize0 in the device descriptor to be not lower than the maxpacket that they set.

[xairy]

Some UDCs also have a minimum device speed they support, e.g. DWC3.

This information is not exposed through usb_gadget though.

The comment for max_speed is also misleading.

[xairy]

So the speed provided to USB_RAW_IOCTL_INIT is rather just a hint, and the UDC might decide to use a different one. Perhaps, we should expose the actual speed of the device as well.

[xairy]

~~It also appears the UDC might set a particular maxpacket value for non-control endpoints, (see calls to dwc2_hsotg_set_ep_maxpacket in dwc2), and Raw Gadget should expose this via USB_RAW_IOCTL_EPS_INFO.~~

~~Or is that the dwc2 driver that needs to be fixed? Other UDCs don't seem to do this.~~

Nevermind, dwc2 takes those values from the USB descriptors.

[xairy]

Issue #73 is related to exposing whether the UDC supports remote wake up.