parisc: Avoid stalled CPU warnings after system shutdown

commit 476e75a44b56038bee9207242d4bc718f6b4de06 upstream.

Commit 73580dac7618 ("parisc: Fix system shutdown halt") introduced an endless
loop for systems which don't provide a software power off function.  But the
soft lockup detector will detect this and report stalled CPUs after some time.
Avoid those unwanted warnings by disabling the soft lockup detector.

Fixes: 73580dac7618 ("parisc: Fix system shutdown halt")
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>