Use the DMA based receive operation instead of the ioread8_rep
based datagram receive when DMA datagrams are supported.

In the receive operation, configure the header to point to the
page aligned VMCI_MAX_DG_SIZE part of the receive buffer
using s/g configuration for the header. This ensures that the
existing dispatch routine can be used with little modification.
Initiate the receive by writing the lower 32 bit of the buffer
to the VMCI_DATA_IN_LOW_ADDR register, and wait for the busy
flag to be changed by the device using a wait queue.

The existing dispatch routine for received  datagrams is reused
for the DMA datagrams with a few modifications:
- the receive buffer is always the maximum size for DMA datagrams
  (IO ports would try with a shorter buffer first to reduce
  overhead of the ioread8_rep operation).
- for DMA datagrams, datagrams are provided contiguous in the
  buffer as opposed to IO port datagrams, where they can start
  on any page boundary
Reviewed-by: Vishnu Dasa <vdasa@vmware.com>
Signed-off-by: Jorgen Hansen <jhansen@vmware.com>
Link: https://lore.kernel.org/r/20220207102725.2742-9-jhansen@vmware.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>