x86: Fix objdump version check in arch/x86/tools/chkobjdump.awk

It says

Warning: objdump version  is older than 2.19
Warning: Skipping posttest.

because it used the wrong field from `objdump -v':

akpm:/usr/src/25> /opt/crosstool/gcc-4.0.2-glibc-2.3.6/x86_64-unknown-linux-gnu/bin/x86_64-unknown-linux-gnu-objdump -v
GNU objdump 2.16.1
Copyright 2005 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License.  This program has absolutely no warranty.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <200912172326.nBHNQaQl024796@imap1.linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>