Fix type clobbering cpuid ext2

Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/target-i386/helper.c b/target-i386/helper.c
index 51f571c..a18dd20 100644
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -1468,7 +1468,7 @@
             /* svm */
             *ecx &= ~4UL;
             /* 3dnow */
-            *edx = ~0xc0000000;
+            *edx &= ~0xc0000000;
         }
         break;
     case 0x80000002: