USB: TI 3410/5052 USB Serial: convert td_open_close_lock to mutex

TI 3410/5052 USB Serial: convert semaphore td_open_close_lock to the mutex
API.

Signed-off-by: Matthias Kaehlcke <matthias.kaehlcke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>