powerpc: Enable lockup and hung task detectors in pseries and ppc64 defeconfigs

As a result of changes to Kconfig files, we no longer enable
the lockup and hung task detectors. Both are very light weight
and provide useful information in the event of a hang, so
reenable them.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>