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 v5.15.63 by commit 1d9e75c3d8cdf7c96a94cb77450d4ee070279e6a, it was introduced in version v5.15.61 by commit ef0f4eeaba2463a77ac5a4e42c30717deb3c7b62. For more details please see the references link.