libgo: fix typo in configure.ac (PCQUANTUm -> PCQUANTUM)
    
    Reviewed-on: https://go-review.googlesource.com/29154

From-SVN: r240146
diff --git a/libgo/configure.ac b/libgo/configure.ac
index f338545..2224f40 100644
--- a/libgo/configure.ac
+++ b/libgo/configure.ac
@@ -222,7 +222,7 @@
     GOARCH_FAMILY=ARM64
     GOARCH_CACHELINESIZE=32
     GOARCH_PHYSPAGESIZE=65536
-    GOARCH_PCQUANTUm=4
+    GOARCH_PCQUANTUM=4
     GOARCH_MINFRAMESIZE=8
     ;;
   arm*-*-* | strongarm*-*-* | ep9312*-*-* | xscale-*-*)