powerpc/powernv: Don't escalate non-existing frozen PE

powerpc/powernv: Don't escalate non-existing frozen PE

Commit ac9fed22 ("powerpc/eeh: Escalate error on non-existing PE")
escalates the frozen state on non-existing PE to fenced PHB. It
was to improve kdump reliability. After that, commit 194fbd03
("powrpc/powernv: Reset PHB in kdump kernel") was introduced to
issue complete reset on all PHBs to increase the reliability of
kdump kernel.

Commit ac9fed22 becomes unuseful and it would be reverted.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>