arm64: defconfig: defconfig update for 3.19

The usual defconfig tweaks, this time:

  - FHANDLE and AUTOFS4_FS to keep systemd happy
  - PID_NS, QUOTA and KEYS to keep LTP happy
  - Disable DEBUG_PREEMPT, as this *really* hurts performance

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>