OvmfPkg/Virtio10Dxe: implement IOMMU-like member functions
OvmfPkg/Virtio10Dxe: implement IOMMU-like member functions

The patch implements the newly added IOMMU-like member functions by
respectively delegating the job to:

- VIRTIO_DEVICE_PROTOCOL.AllocateSharedPages() ->
    EFI_PCI_IO_PROTOCOL.AllocateBuffer()

- VIRTIO_DEVICE_PROTOCOL.FreeSharedPages() ->
    EFI_PCI_IO_PROTOCOL.FreeBuffer()

- VIRTIO_DEVICE_PROTOCOL.MapSharedBuffer() ->
    EFI_PCI_IO_PROTOCOL.Map()

- VIRTIO_DEVICE_PROTOCOL.UnmapSharedBuffer() ->
    EFI_PCI_IO_PROTOCOL.Unmap()

Suggested-by: Laszlo Ersek <7437296077edea1cb64451c122c4dac071f0cfbc@redhat.com>
Cc: Ard Biesheuvel <66d3c5fdaeea7ff1f996ad04f2c45e08ab38e2f5@linaro.org>
Cc: Jordan Justen <a79006884ba9cf5f4f7fcbb92a15b208780d8c97@intel.com>
Cc: Tom Lendacky <bcbe2d8614c98cf419bfc4320d4a7a260d53de8f@amd.com>
Cc: Laszlo Ersek <7437296077edea1cb64451c122c4dac071f0cfbc@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Brijesh Singh <6c1ba716601dd19ee463759bfdaf6de1e69b2b21@amd.com>
Reviewed-by: Laszlo Ersek <7437296077edea1cb64451c122c4dac071f0cfbc@redhat.com>
Regression-tested-by: Laszlo Ersek <7437296077edea1cb64451c122c4dac071f0cfbc@redhat.com>

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