staging: unisys: visorhid: correctly map keys with extended scancodes

The most-noticed key that wasn't being mapped correctly was Right-Alt,
which is the AltGr key on many non-US keyboards, used to select many
extended characters.

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>