fix(cros-kernel/x86_64_defconfig) disable ext3 and ext2

ext4 can, and should, handle both of these filesystems now, so have it
do so.
fix(cros-kernel/x86_64_defconfig) enable CONFIG_MEMCG_SWAP_ENABLED

This is requested so that cgroups can swap properly.
Merge pull request #21 from gregkh/kernel_slimdown

fix(cros-kernel/x86_64_defconfig) disable ext3 and ext2