Fix bison parsing

Changes from me to switch the order in which we choose to use yacc or
bison, default to using bison if we have it.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/configure b/configure
index 21b8739..0620d58 100755
--- a/configure
+++ b/configure
@@ -1262,14 +1262,14 @@
 if test -x "$LEX" ; then
   lex="yes"
 fi
-YACC=$(which yacc 2> /dev/null)
+YACC=$(which bison 2> /dev/null)
 if test -x "$YACC" ; then
   yacc="yes"
+  yacc_is_bison="yes"
 else
-  YACC=$(which bison 2> /dev/null)
+  YACC=$(which yacc 2> /dev/null)
   if test -x "$YACC" ; then
     yacc="yes"
-    yacc_is_bison="yes"
   fi
 fi
 if test "$yacc" = "yes" && test "$lex" = "yes" ; then