Loader tunable fetching has been broken on stable/10 since ix(4) rewrite
introduced by r280182. FreeBSD-head doesn't need TUNABLE_INT() now with
SYSCTL_INT() but stable/10 still does.
Note: This is a direct commit to stable/10.

PR: 201644
Reviewed by: erj
Approved by: re (gjb)
Sponsored by: Limelight Networks