Enable generating PPC pre-increment (r+imm) instructions by default.

It seems that this no longer causes test suite failures on PPC64 (after r157159),
and often gives a performance benefit, so it can be enabled by default.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157911 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/CodeGen/PowerPC/stwu8.ll b/test/CodeGen/PowerPC/stwu8.ll
index fabf763..897bfc6 100644
--- a/test/CodeGen/PowerPC/stwu8.ll
+++ b/test/CodeGen/PowerPC/stwu8.ll
@@ -1,4 +1,4 @@
-; RUN: llc -enable-ppc-preinc < %s | FileCheck %s
+; RUN: llc < %s | FileCheck %s
 target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v128:128:128-n32:64"
 target triple = "powerpc64-unknown-linux-gnu"