Replace 0x7f literals with PCI_HEADER_TYPE_MASK.

Link: https://lore.kernel.org/r/20231124090919.23687-2-ilpo.jarvinen@linux.intel.comSigned-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>