grouper: update prebuilt kernel 6ff7a51 Revert "tegra3_android_defconfig: switch to SLUB" b/18596108 GFXBench3 TRex test report unsupported on LRX22D Change-Id: Icfecff7f5eef1d09cd56c846ea8ea0e4b7720c6d Signed-off-by: Iliyan Malchev <malchev@google.com>