Input: psmouse - fix new device detection logic

Reported to fix http://bugs.gentoo.org/130846Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Cc: Daniel Drake <dsd@gentoo.org>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>