staging: unisys: visorinput: handle_locking_key() simplifications

By directly returning for the error-case, a test was eliminated.  Also,
the old_state variable was removed as it was not necessary, and some
redundant parens were removed.

Signed-off-by: Tim Sell <Timothy.Sell@unisys.com>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>