Sort MK_DTRACE and MK_ZFS options

Presumably these were under MK_CDDL at some point, but these days
src.opts.mk takes care of setting them to "no" when MK_CDDL is.

Reviewed by: emaste, imp, netchild
Pull Request: https://github.com/freebsd/freebsd-src/pull/896

(cherry picked from commit a62cefbb5c835eb17057bca98106f325b13bdead)