linuxkpi: errno: Add EHWPOISON
Needed by drm-kmod.
Reviewed by: bz, hselasky
Obtained from: drm-kmod
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D36017
(cherry picked from commit 2d4b17685fd2891ffc28590a408df4b96d218b05)