Butterfly: switch to kernel 3.4

This changes Butterfly back to kernel 3.4 due to issues
with 3.8 kernels on SandyBridge platforms

BUG=chromium:317968
TEST=make sure the resulting image has a 3.4 kernel (uname -a)

Change-Id: Ic19e7e1cfde451173a6c9e8fc47ae919f90e31aa
Reviewed-on: https://chromium-review.googlesource.com/180727
Reviewed-by: Olof Johansson <olofj@chromium.org>
Commit-Queue: Olof Johansson <olofj@chromium.org>
Tested-by: Olof Johansson <olofj@chromium.org>
diff --git a/overlay-butterfly/make.conf b/overlay-butterfly/make.conf
index 2c52b66..2eb68fd 100644
--- a/overlay-butterfly/make.conf
+++ b/overlay-butterfly/make.conf
@@ -7,9 +7,10 @@
 
 USE="${USE} bluetooth butterfly legacy_kerboard lockvt"
 
-# Use kernel-next with 3.4 wifi stack
-USE="${USE} kernel_next wireless34"
 # Use 32-bit AU post-install binary to accomodate 32 --> 64 AU
 USE="${USE} 32bit_au"
 
+# This USE flag is obsolete on 3.8+ kernel
+USE="${USE} realtekpstor"
+
 MARCH_TUNE="-march=core2 -mtune=generic"