padata: Put CPU offline callback in ONLINE section to allow failure

padata: Put CPU offline callback in ONLINE section to allow failure

syzbot reported the following warning:

    DEAD callback error for CPU1
    WARNING: kernel/cpu.c:1463 at _cpu_down+0x759/0x1020 kernel/cpu.c:1463, CPU#0: syz.0.1960/14614

at commit 4ae12d8bd9a8 ("Merge tag 'kbuild-fixes-7.0-2' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux")
which tglx traced to padata_cpu_dead() given it's the only
sub-CPUHP_TEARDOWN_CPU callback that returns an error.

Failure isn't allowed in hotplug states before CPUHP_TEARDOWN_CPU
so move the CPU offline callback to the ONLINE section where failure is
possible.

Fixes: 894c9ef9780c ("padata: validate cpumask without removed CPU during offline")
Reported-by: syzbot+123e1b70473ce213f3af@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/69af0a05.050a0220.310d8.002f.GAE@google.com/
Debugged-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>