syscalls: add __NR_kcmp syscall to generic unistd.h

syscalls: add __NR_kcmp syscall to generic unistd.h

Commit d97b46a64 added a new syscall (__NR_kcmp) to support checkpoint
restore. It is currently x86-only, but that restriction will be removed
in a subsequent patch. Unfortunately, the kernel checksyscalls script
had a bug which suppressed any warning to other architectures that the
kcmp syscall was not implemented. A patch to checksyscalls is being
tested in linux-next and other architectures are seeing warnings about
kcmp being unimplemented.

This patch adds __NR_kcmp to <asm-generic/unistd.h> so that kcmp is
wired in for architectures using the generic syscall list.

Signed-off-by: Mark Salter <msalter@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>