UBUNTU: SAUCE: SECCOMP: asm/syscall.h: add syscall_get_arch

UBUNTU: SAUCE: SECCOMP: asm/syscall.h: add syscall_get_arch

Adds a stub for a function that will return the AUDIT_ARCH_*
value appropriate to the supplied task based on the system
call convention.

For audit's use, the value can generally be hard-coded at the
audit-site.  However, for other functionality not inlined into
syscall entry/exit, this makes that information available.
seccomp_filter is the first planned consumer and, as such,
the comment indicates a tie to HAVE_ARCH_SECCOMP_FILTER.  That
is probably an unneeded detail.

v14: rebase/nochanges
v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: rebase on to linux-next
v11: fixed improper return type
v10: introduced

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Suggested-by: Roland McGrath <mcgrathr@chromium.org>
Signed-off-by: Will Drewry <wad@chromium.org>
Signed-off-by: Kees Cook <kees@ubuntu.com>