remoteproc: core: Auto select rproc-virtio device id

With multiple remoteproc device, there will below error:

sysfs: cannot create duplicate filename '/bus/platform/devices/rproc-virtio.0'

The rvdev_data.index is duplicate, that cause issue, so
need to use the PLATFORM_DEVID_AUTO instead. After fixing
device name it becomes something like:
/bus/platform/devices/rproc-virtio.2.auto

Fixes: 1d7b61c0 ("remoteproc: virtio: Create platform device for the remoteproc_virtio")
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Reviewed-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
Tested-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/1666100644-27010-1-git-send-email-shengjiu.wang@nxp.com


[Fixed typographical error in comment block]
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>