configure: add some MIPS CPUs

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@18872 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

configure

@@ -1847,6 +1847,9 @@ if test $cpu != "generic"; then
         bf*)
             add_cflags -mcpu=$cpu
         ;;
+        mips*|[45]k*|[237]4k*|m4k|r*000|loongson2[ef])
+            add_cflags -march=$cpu
+        ;;
         *)
             echo "WARNING: Unknown CPU \"$cpu\", ignored."
         ;;