On a PCI type HV uart, the bdf value is in a union together with
mmio_base_vaddr, then the value would be overridden by mmio_base_addr
in uart16550_init(), result in is_pci_dbg_uart() returns a wrong value
and then uart hang.
Tracked-On: #5288
Signed-off-by: Victor Sun <victor.sun@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>