VMCI: dma dg: register dummy IRQ handlers for DMA datagrams

Register dummy interrupt handlers for DMA datagrams in preparation for
DMA datagram receive operations.

Reviewed-by: Vishnu Dasa <vdasa@vmware.com>
Signed-off-by: Jorgen Hansen <jhansen@vmware.com>
Link: https://lore.kernel.org/r/20220207102725.2742-6-jhansen@vmware.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>