phb3: Lock the PHB on set_xive callbacks
phb3: Lock the PHB on set_xive callbacks

Those are called by the interrupts core and thus skip the locking
implicit in the PCI opal calls.

However IODA table access can be racy, so make sure we lock the PHB.

Signed-off-by: Benjamin Herrenschmidt
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

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