remoteproc: Fix various kernel-doc warnings

Fix all the kernel-doc warnings in various remoteproc core files.
Some of them just needed a formatting cleanup change, while others
needed the Return statement to be added, or documenting the missed
structure elements.

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suman Anna <s-anna@ti.com>
Link: https://lore.kernel.org/r/20210519180304.23563-3-s-anna@ti.com


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