MFC r320390:

With r318394 seems it breaks gpart(8) in some embedded systems such like PCEngines,
RPI1-B, Alix and APU2 boards as well as NanoBSD with the following message:

vnode_pager_generic_getpages_done: I/O read error 5

Seems the breakage was because it was missed to include acr in glabel update.

Reported by: Peter Blok <pblok@bsd4all.org>,

		madpilot, imp and trasz.

Reviewed by: trasz
Tested by: Peter Blok and madpilot.
Sponsored by: iXsystems, Inc.
Differential Revision: https://reviews.freebsd.org/D11365