Input: gamecon - reference correct pad in gc_psx_command()

Otherwise we won't see any events from the gamepad.
Addresses https://bugzilla.kernel.org/show_bug.cgi?id=16408



Reported-and-tested-by: Eugene Yudin <eugene.yudin@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>