zfs: update zfs_config.h to match OpenZFS gf11b09dec

Update zfs_config.h to match latest merge in FreeBSD

The version string is declared as 2.0.0-FreeBSD_gf11b09dec to provide
more information about the loaded module:

• the OpenZFS version in base is 2.0
• we are using the in tree-module ("FreeBSD")
• the last merged OpenZFS git revision ("gf11b09dec")

With future merges the git revision tag should be updated.
As we are merging from OpenZFS master branch and already include features
like dRAID, referencing patchlevel releases (2.0.1, 2.0.2) is pointless.

Reviewed by: freqlabs
Differential Revision: https://reviews.freebsd.org/D28447

(cherry picked from commit 8fb966790e1c87276cc26932efee1b29c046cb8a)