ANDROID: usb: gadget: mtp: Add MTP/PTP function

USB gadget function driver used by the Android framework to
implement the MTP and PTP protocols. It creates a character device
that provides an interface for fast transfer of files and
supports transferring files greater than 4GB.

Change-Id: I2d8f2c37029fb37d8deb791d04eb7346f94f5adb
Signed-off-by: Mike Lockwood <lockwood@android.com>