Honor WITHOUT_LIB32 on mips64.

The closing paren for the list of architectures that should enable LIB32
by default was in the wrong place resulting in LIB32 always be enabled on
mips64 regardless of WITH_LIB32/WITHOUT_LIB32.

Submitted by: Alex Richardson <Alexander.Richardson@cl.cam.ac.uk>
Obtained from: CheriBSD
Sponsored by: DARPA / AFRL