remoteproc: Split rproc_ops allocation from rproc_alloc()

Make the rproc_ops allocation a function on its own in an effort
to clean up function rproc_alloc().

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20200420231601.16781-4-mathieu.poirier@linaro.org


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