staging: serqt_usb2: remove driver

Remove the driver as it hasn't been cleaned up and it doesn't look like
anyone is going to work on it anymore. This can be reverted if someone
wants to work to fix the remaining issues the driver has.

Signed-off-by: Kristina Martšenko <kristina.martsenko@gmail.com>
Cc: Bill Pemberton <wfp5p@virginia.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>