Revert "debian/sysdeps/mips{n32,}{r6,}{el,}.mk: build with --param...

Revert "debian/sysdeps/mips{n32,}{r6,}{el,}.mk: build with --param ggc-min-expand=10 to avoid virtual memory exhaustion when compiling test-tgmath3.o."

This reverts commit 60f9422a. That was a
previous try, which does not the right thing when cross-compiling.