Revert "arm64: add seccomp support"

This reverts commit 923b5e25.
[djkurtz: trivial conflict fixup in arch/arm64/Kconfig]

To be replaced with arm64 seccomp from mainline v3.19.

Change-Id: Icad82d42b1b3d755c8130657cc3675d460320b86
Signed-off-by: Daniel Kurtz <djkurtz@google.com>