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 v4.14.291 by commit 6f75057c21eab12c6ccb7f06f859641a6edfab99, it was introduced in version v4.14.291 by commit a79e4395619c926ea7e828b2023c0fbe2776385b. For more details please see the references link.