android: configs: base: enable configfs gadget functions

android: configs: base: enable configfs gadget functions

Now that Android is moving towards ConfigFS based USB gadgets,
lets enable USB_CONFIGFS and relevant Android gadget functions
instead of obsolete USB_G_ANDROID composite driver which doesn't
exist now.

Enabled following ConfigFS gadget functions:

F_FS            for ADB
F_MTP/PTP       for MTP/PTP
F_ACC           for Android USB Accessory
F_AUDIO_SRC     for USB Audio Source
F_MIDI          for MIDI, and
CONFIGFS_UEVENT for communicating USB state change notifications to userspace.

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>