powerpc/configs: Re-enable HARD/SOFT lockup detectors

In commit 05a4a952 ("kernel/watchdog: split up config options"),
CONFIG_LOCKUP_DETECTOR was split into two separate config options,
CONFIG_HARDLOCKUP_DETECTOR and CONFIG_SOFTLOCKUP_DETECTOR.

Our defconfigs still have CONFIG_LOCKUP_DETECTOR=y, but that is no longer
user selectable, and we don't mention the new options, so we end up with
none of them enabled.

So update the defconfigs to turn on the new SOFT and HARD options, the
end result being the same as what we had previously.

Fixes: 05a4a952 ("kernel/watchdog: split up config options")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>