wayland/libinput-openbsd: secondary wsmouse device requires fbtab entry

Dear OpenBSD ports,

I've encountered (and resolved) an issue when attempting to use the
TrackPoint on my ThinkPad T440p in Sway where using it does not seem to
work.

After looking at the Sway logs it seemed, other than wsmouse0, none of
the other mouse devices were able to be opened, leading me to append
wsmouse1 (which is the device the TrackPoint appears as) to allowed
devices on ttyC0 in /dev/fbtab.

00:00:01.130 [wlr] [backend/session/session.c:331] Failed to open device: '/dev/wsmouse1': Permission denied

This also means that external mice which take on wsmouse2 or other, may
not work by default either.

Because I didn't see any documentation or README on the libinput
package, I wanted to know which approach should be taken to let the user
know of this quirk and where a change could belong.