remoteproc: imx_rproc: ignore mapping vdev regions

vdev regions are vdev0vring0, vdev0vring1, vdevbuffer and similar.
They are handled by remoteproc common code, no need to map in imx
rproc driver.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/1615029865-23312-10-git-send-email-peng.fan@oss.nxp.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>