USB: serial: Add support for new composition framework

Following command needs to be given to enable SERIAL
transports. This has to be done once before selecting serial
function.
For TTY-DUN, TTY-NMEA:
 echo tty,tty >
	/sys/class/android_usb/android0/f_serial/transports

For SDIO-DUN, TTY-NMEA:
 echo sdio,tty >
	/sys/class/android_usb/android0/f_serial/transports

Signed-off-by: Manu Gautam <mgautam@codeaurora.org>

Conflicts:

	arch/arm/mach-msm/include/mach/usb_gadget_fserial.h