core/opal: abort in case of re-entrant OPAL call
core/opal: abort in case of re-entrant OPAL call

The stack is already destroyed by the time we get here, so there
is not much point continuing.

Signed-off-by: Nicholas Piggin <24829078df5003d9dd1dd871ca2aeb0b1cf95ef4@gmail.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

qemu/skiboot,open-power/skiboot,stewart-ibm/skiboot,stewart-ibm/skiboot,qemu/skiboot,shenki/skiboot,shenki/skiboot,qemu/skiboot,legoater/skiboot,open-power/skiboot,open-power/skiboot,qemu/skiboot,legoater/skiboot,open-power/skiboot,shenki/skiboot,qemu/skiboot,legoater/skiboot,legoater/skiboot,legoater/skiboot,shenki/skiboot,open-power/skiboot,stewart-ibm/skiboot,shenki/skiboot