wsp(4): Add evdev support.

Reviewed by: hselasky
Tested by: Greg V, Constantin Furst<constantin_AT_fuersten_DOT_info>
PR: 252236
Differential revision: https://reviews.freebsd.org/D31653

(cherry picked from commit 8d73071c47ff1f911bdaec6356f37feb4e3b7cb5)