USB: ssu100: rework logic for TIOCMIWAIT

Rework the logic for TIOCMIWAIT to use wait_event_interruptible.

This also adds support for TIOCGICOUNT.

Signed-off-by: Bill Pemberton <wfp5p@virginia.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>