moused(8): Start moused with devd

It is appeared that currently starting of moused does not depend on
moused_enable variable value in rc.conf. That leads to missing USB mice
support in default configuration. Start moused in traditional per
device mode with devd to follow POLA.

One daemon per system mode still can be enabled with setting of
moused_port="auto"
moused_nondefault_enable="NO"
variables in /etc/rc.conf

To revert to sysmouse mode add moused_type="sysmouse" to /etc/rc.conf

Reported by: many
Requested by: glebius
Reviewed by: glebius
MFC after: 1 day
Differential Revision: https://reviews.freebsd.org/D52430