jail.h: Fix whitespace in the param macros declaration block

Reviewed by: jamie
Approved by: markj (mentor)
MFC after: 5 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D46900

(cherry picked from commit f8fe6bc73bbbced506a02ed88783c0c0bb9b49e4)