Move functions related to the management of the rproc_vdev
structure in the remoteproc_virtio.c.
The aim is to decorrelate as possible the virtio management from
the core part.

Due to the strong correlation between the vrings and the resource table
the rproc_alloc/parse/free_vring functions are kept in the remoteproc core.
Signed-off-by: NArnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Link: https://lore.kernel.org/r/20220921135044.917140-4-arnaud.pouliquen@foss.st.comSigned-off-by: NMathieu Poirier <mathieu.poirier@linaro.org>