arm64: add seccomp support

Note: This patch is from v6 of Takahiro's proposed
"arm64: add seccomp support" patchset (leecam@google.com)

secure_computing() is called first in syscall_trace_enter() so that a system
call will be aborted quickly without doing succeeding syscall tracing,
contrary to other cases, if seccomp rules deny that system call.

On compat task, syscall numbers for system calls allowed in seccomp mode 1
are different from those on normal tasks, and so _NR_seccomp_xxx_32's need
to be redefined.

Signed-off-by: AKASHI Takahiro <takahiro.akashi <at> linaro.org>
Git-commit: 210957c2bb3b4d111963bb296e2c42beb8721929
Git-repo: https://android.googlesource.com/kernel/common.git


[imaund@codeaurora.org: Resolved context conflicts]
Signed-off-by: Ian Maund <imaund@codeaurora.org>
Change-Id: I7a55d9a5cde17105ba85e5fefa9a7013d633b48c
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>