remoteproc: core: Make the loaded resource table optional

Remote processors like the ones found in the Qualcomm SoCs does not have
a resource table passed to them, so make it optional by only populating
it if it does exist.

Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>