GSD-2022-1005121 powerpc/pci: Fix get_phb_number() locking

powerpc/pci: Fix getphbnumber locking This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v5.19.4 by commit 90f195c01a2e8d8da6281791617e21109719c981...