powerpc64le: readd COMPAT_FREEBSD11 and COMPAT_FREEBSD12

lang/rust needs COMPAT_FREEBSD11 to build, even though powerpc64le itself is
supported only since 13.0.
I also corrected a comment, because if we ever have lib32 for powerpc64le,
it will be for powerpcle.

Reviewed by: bdragon (on IRC)
Approved by: gjb (re)

(cherry picked from commit 8b804ee616b4c8810015b69e37e31ef0c4161511)