configure: fix bug to ensure that HAVE_VSX is only enabled when HAVE_ALTIVEC is enabled and in LE environment

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

configure

@@ -4390,7 +4390,7 @@ EOF
 od -t x1 $TMPO | grep -q '42 *49 *47 *45' && enable bigendian
 
 if  [ "$cpu" = "power7" ] || [ "$cpu" = "power8" ] ;then
-    if ! enabled bigendian ;then
+    if ! enabled bigendian && enabled altivec ;then
         enable vsx
     fi
 fi