tools headers UAPI: Sync linux/perf_event.h with the kernel sources

tools headers UAPI: Sync linux/perf_event.h with the kernel sources

To pick the trivial change in:

  cb1c4aba055f928f ("perf: Add new macros for mem_hops field")

Just comment source code alignment.

This silences this perf build warning:

  Warning: Kernel ABI header at 'tools/include/uapi/linux/perf_event.h' differs from latest version at 'include/uapi/linux/perf_event.h'
  diff -u tools/include/uapi/linux/perf_event.h include/uapi/linux/perf_event.h

Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/lkml/YflPKLhu2AtHmPov@kernel.org/
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>