devices: pci: use header type 0 for host bridge

Previously, we were using header type 1 (which is meant to be used only
for PCI-to-PCI bridges), which upsets the Linux PCI probing code:

pci 0000:00:00.0: ignoring class 0x060000 (doesn't match header type 01)

Switch to the standard type 0 header instead, which makes the kernel
happy and matches what real hardware uses.

BUG=None
TEST=Boot vm_kernel (Linux 4.19) in crosvm

Change-Id: I33d10bda39edf6d949827963cebbfe66c9147ea2
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1660892
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Dylan Reid <dgreid@chromium.org>

devices/src/pci/pci_root.rs

@@ -58,7 +58,7 @@ impl PciRoot {
                     PciClassCode::BridgeDevice,
                     &PciBridgeSubclass::HostBridge,
                     None,
-                    PciHeaderType::Bridge,
+                    PciHeaderType::Device,
                     0,
                     0,
                 ),