rust: pci: display symbolic PCI vendor names

rust: pci: display symbolic PCI vendor names

The Display implementation for Vendor was forwarding directly to Debug
printing, resulting in raw hex values instead of PCI Vendor strings.

Improve things by doing a stringify!() call for each PCI Vendor item.
This now prints symbolic names such as "NVIDIA", instead of
"Vendor(0x10de)". It still falls back to Debug formatting for unknown
class values.

Suggested-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
[ Remove #[inline] for Vendor::fmt(). - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>