Noticed by the build system, that emitted this warning:

  Warning: x86_64's syscall_64.tbl differs from kernel

This was due to the wiring up of the recently added preadv2 & pwritev2
syscalls to the compat code, which hadn't been done by the patch
introducing those syscalls: 4babf2c5 ("x86: wire up preadv2 and
pwritev2").

The patch doing the compat wiring was:

  482dd2ef ("x86/syscalls: Wire up compat readv2/writev2 syscalls")

This just silences the perf build warning, as compat syscalls still
can't be supported in 'perf trace´ due to limitations in the
raw_syscalls:sys_{enter,exit} tracepoints it relies on.
Reported-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-4dm8eoy0wslgtwqdhz64ods0@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>