staging: unisys: visorinput: register & use input_dev open() and close()

Registration of visorinput_open() and visorinput_close() for each device
allow us to eliminate unnecessary activity when nobody in user-land
cares.

Signed-off-by: Tim Sell <Timothy.Sell@unisys.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>