tools include UAPI: Sync x86's syscalls_64.tbl, generic unistd.h and fcntl.h to pick up openat2 and pidfd_getfd

  fddb5d43 ("open: introduce openat2(2) syscall")
  9a2cef09 ("arch: wire up pidfd_getfd syscall")

We also need to grab a copy of uapi/linux/openat2.h since it is now
needed by fcntl.h, add it to tools/perf/check_headers.h.

  $ diff -u tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl
  --- tools/perf/arch/x86/entry/syscalls/syscall_64.tbl	2019-12-20 16:43:57.662429958 -0300
  +++ arch/x86/entry/syscalls/syscall_64.tbl	2020-02-10 16:36:22.070012468 -0300
  @@ -357,6 +357,8 @@
   433	common	fspick			__x64_sys_fspick
   434	common	pidfd_open		__x64_sys_pidfd_open
   435	common	clone3			__x64_sys_clone3/ptregs
  +437	common	openat2			__x64_sys_openat2
  +438	common	pidfd_getfd		__x64_sys_pidfd_getfd

   #
   # x32-specific system call numbers start at 512 to avoid cache impact
  $

Update tools/'s copy of that file:

  $ cp arch/x86/entry/syscalls/syscall_64.tbl tools/perf/arch/x86/entry/syscalls/syscall_64.tbl

See the result:

  $ diff -u /tmp/build/perf/arch/x86/include/generated/asm/syscalls_64.c.before /tmp/build/perf/arch/x86/include/generated/asm/syscalls_64.c
  --- /tmp/build/perf/arch/x86/include/generated/asm/syscalls_64.c.before	2020-02-10 16:42:59.010636041 -0300
  +++ /tmp/build/perf/arch/x86/include/generated/asm/syscalls_64.c	2020-02-10 16:43:24.149958337 -0300
  @@ -346,5 +346,7 @@
   	[433] = "fspick",
   	[434] = "pidfd_open",
   	[435] = "clone3",
  +	[437] = "openat2",
  +	[438] = "pidfd_getfd",
   };
  -#define SYSCALLTBL_x86_64_MAX_ID 435
  +#define SYSCALLTBL_x86_64_MAX_ID 438
  $

Now one can use:

  perf trace -e openat2,pidfd_getfd

To get just those syscalls or use in things like:

  perf trace -e open*

To get all the open variant (open, openat, openat2, etc) or:

  perf trace pidfd*

To get the pidfd syscalls.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Sargun Dhillon <sargun@sargun.me>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>