usb: gadget: f_tcm: convert to new function interface with backward compatibility

usb: gadget: f_tcm: convert to new function interface with backward compatibility

Converting tcm to the new function interface requires converting
USB tcm's function code and its users.

This patch converts the f_tcm.c to the new function interface.

The file can be now compiled into a separate module usb_f_tcm.ko.

The old function interface is provided by means of preprocessor conditional
directives. After all users are converted, the old interface can be
removed.

Signed-off-by: Andrzej Pietrasiewicz <[email protected]>
Acked-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Nicholas Bellinger <[email protected]>