USB: gadget: f_mtp: Add PTP variant of MTP USB function

This is the same as MTP but with PTP interface descriptor.
Also removed obsolete ioctl for switching between MTP and PTP mode

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

include/linux/usb/f_mtp.h

@@ -18,10 +18,6 @@
 #ifndef __LINUX_USB_F_MTP_H
 #define __LINUX_USB_F_MTP_H
 
-/* Constants for MTP_SET_INTERFACE_MODE */
-#define MTP_INTERFACE_MODE_MTP  0
-#define MTP_INTERFACE_MODE_PTP  1
-
 
 struct mtp_file_range {
 	/* file descriptor for file to transfer */
@@ -45,8 +41,6 @@ struct mtp_event {
  * The file is created if it does not exist.
  */
 #define MTP_RECEIVE_FILE           _IOW('M', 1, struct mtp_file_range)
-/* Sets the driver mode to either MTP or PTP */
-#define MTP_SET_INTERFACE_MODE     _IOW('M', 2, int)
 /* Sends an event to the host via the interrupt endpoint */
 #define MTP_SEND_EVENT             _IOW('M', 3, struct mtp_event)