x86_64/vsyscall: Fix warn_bad_vsyscall log output

x86_64/vsyscall: Fix warn_bad_vsyscall log output

This commit in Linux 3.6:

    commit b30bfe911417227f106780eb365a309441973fe5
    Author: Joe Perches <joe@perches.com>
    Date:   Mon May 21 19:50:07 2012 -0700

        x86/debug: Add KERN_<LEVEL> to bare printks, convert printks to pr_<level>

caused warn_bad_vsyscall to output garbage in the middle of the
line.  Revert the bad part of it.

The printk in question isn't actually bare; the level is "%s".

The bug this fixes is purely cosmetic; backports are optional.

Cc: <stable@vger.kernel.org> # v3.6+
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/03eac1f24110bbe496ecc12a4df467e0d88466d4.1406330947.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>