This is the name of the structure on Linux. I'm about to expose it through linuxkpi as an opaque type. Therefore it allows to use it directly without further compatibility code in linuxkpi.
This structure is otherwise internal to sys/kern/sys_eventfd.c and not used anywhere else. Thus it is safe to change its name without breaking anything.
This is a requirement to the following patch to drm-kmod:
https://github.com/freebsd/drm-kmod/pull/358
Sponsored by: The FreeBSD Foundation