remoteproc: configure IOMMU only if device address requested

If there is no IOMMU associate to remote processor device,
remoteproc_core won't be able to satisfy device address requested
in firmware resource table.
Return an error as configuration won't be coherent.

Signed-off-by: Loic Pallardy <loic.pallardy@st.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>