usb: ftdi-elan: Delete driver

usb: ftdi-elan: Delete driver

This driver didn't see real maintainance since several years. It has
several trivial issues (check $(scripts/checkpatch.pl -f
drivers/usb/misc/ftdi-elan.c)) and some harder ones (difficult locking,
explict kref handling, ...). Also today it's hard to find hardware to
make actually use of such a card and I suspect the driver is completely
unused.

So remove it.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20230321150919.351947-1-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>