OvmfPkg: drop redundant VendorID check in VirtioMmioDeviceLib
There is a DEBUG warning printout in VirtioMmioDeviceLib if the current
device's VendorID does not match the traditional 16-bit Red Hat PCIe
vendor ID used with virtio-pci. The virtio-mmio vendor ID is 32-bit and
has no connection to the PCIe registry.
Most specifically, this causes a bunch of noise when booting an AArch64
QEMU platform, since QEMU's virtio-mmio implementation used 'QEMU' as
the vendor ID:
VirtioMmioInit: Warning:
The VendorId (0x554D4551) does not match the VirtIo VendorId (0x1AF4).