hammerhead: update prebuilt kernel

20dcde6 uid_cputime: Iterates over all the threads instead of processes.
4839012 USB: u_ether: Set complete handler before queueing to endpoint

Linux version 3.4.0-g20dcde6 (android-build@vpba11.mtv.corp.google.com)
(gcc version 4.8 (GCC) ) #1 SMP PREEMPT Fri Jul 31 22:51:00 UTC 2015

Bug: 18541764
Bug: 22833116
Change-Id: If8adf7d0252bf883a32b3186fe613269e5c0a5c4
Signed-off-by: Thierry Strudel <tstrudel@google.com>
diff --git a/zImage-dtb b/zImage-dtb
index 533dd9c..5b4048a 100644
--- a/zImage-dtb
+++ b/zImage-dtb
Binary files differ