perf unwind: Fix libunwind build failure on i386 systems

Naresh Kamboju reported, that on the i386 build pr_err()
doesn't get defined properly due to header ordering:

  perf-in.o: In function `libunwind__x86_reg_id':
  tools/perf/util/libunwind/../../arch/x86/util/unwind-libunwind.c:109:
  undefined reference to `pr_err'

Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>