First version of RPMSG working on Popcorn Linux. Basic rpmsg features
works with two vrings. This impementation uses a producer/consumer model
wherein the tx and rx rings are reversed on host and remote
processor's. This way we both ends runs the same rpmsg code. Tx logic
of original rpmsg code is modified to work this way.

Sighned-off-by: Ajo Jose Panoor <ajopanoor@gmail.com>

 On branch dummy_lproc_rpmsg
 Changes to be committed:
	modified:   drivers/remoteproc/dummy_localproc.c
	modified:   drivers/remoteproc/dummy_remoteproc.c
	modified:   drivers/remoteproc/localproc_core.c
	modified:   drivers/rpmsg/virtio_rpmsg_bus.c
	modified:   drivers/virtio/virtio_ring.c