perf s390: Generate system call table from asm/unistd.h

This should speed up accessing new system calls introduced with
the kernel rather than waiting for libaudit updates to include
them.

Committer testing:

  $ rm -rf /tmp/build/perf
  $ mkdir /tmp/build/perf
  $ make srctree=/home/acme/git/perf -C tools/perf/arch/s390 OUTPUT=/tmp/build/perf/ archheaders
  make: Entering directory '/home/acme/git/perf/tools/perf/arch/s390'
  /bin/sh '/home/acme/git/perf/tools/perf/arch/s390/entry/syscalls//mksyscalltbl' 'cc' /home/acme/git/perf/tools/arch/s390/include/uapi/asm/unistd.h > /tmp/build/perf/arch/s390/include/generated/asm/syscalls_64.c
  make: Leaving directory '/home/acme/git/perf/tools/perf/arch/s390'
  $ head -5 /tmp/build/perf/arch/s390/include/generated/asm/syscalls_64.c
  static const char *syscalltbl_s390_64[] = {
	[1] = "exit",
	[2] = "fork",
	[3] = "read",
	[4] = "write",
  $ tail -5 /tmp/build/perf/arch/s390/include/generated/asm/syscalls_64.c
	[378] = "s390_guarded_storage",
	[379] = "statx",
	[380] = "s390_sthyi",
  };
  #define SYSCALLTBL_S390_64_MAX_ID 380
  $

Now to plug this into 'perf trace' proper.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Reviewed-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: linux-s390@vger.kernel.org
LPU-Reference: 1512635281-20733-2-git-send-email-brueckner@linux.vnet.ibm.com
Link: https://lkml.kernel.org/n/tip-h5km60rdg3rqxvsys85q50l3@git.kernel.org


[ split from a larger patch ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>