Input: mousedev - allow disabling even without CONFIG_EXPERT

Moust (if not all) modern software, including X, uses /dev/eventX rather than
the legacy /dev/mouseX devices. It therefore makes sense for general-purpose
(distro) kernels to use MOUSEDV=m (or even n), so let's drop the EXPERT=y
requirement.

Signed-off-by: Tom Gundersen <teg@jklm.no>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>