UBUNTU: SAUCE: powerpc/xive: Fix trying to "push" an already active pool VP

BugLink: https://bugs.launchpad.net/bugs/1763386



When setting up a CPU, we "push" (activate) a pool VP for it.

However it's an error to do so if it already has an active
pool VP.

This happens when doing soft CPU hotplug on powernv since we
don't tear down the CPU on unplug. The HW flags the error which
gets captured by the diagnostics.

Fix this by making sure to "pull" out any already active pool
first.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Link: https://patchwork.ozlabs.org/patch/897035/


Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>