This updates zfs_config.h to match the latest merge in FreeBSD
The version is declared as 2.0.0-FreeBSD_gf11b09dec, this should reflect that:
- we are dealing with OpenZFS 2.0
- this is the in-tree module (wording "FreeBSD")
- last merged OpenZFS git revision ("gf11b09dec")
The version string is of course up to discussion.