usbgadget missing from MACHINE_FEATUREs

[auzroz]

Description

In initial commit cc91d81, usbgadget was present in the conf/machine/raspberrypi.conf file. In commit 5c8d2c0, it was removed under the merge comment of "raspberrypi.conf: is not a usb gadget ", but I can't find any discussion on this topic. the pi family is fully capable of being a usbgadget, wondering what the historical reason for this was and whether usbgadget should be mainline supported or left to individual customization.

Describe the results you received:

usbgadget support isn't available by default.

Describe the results you expected:

usbgadget support enabled as a MACHINE_FEATURE by default.