remoteproc: Introducing function rproc_actuate()

Introduce function rproc_actuate() that provides the same
functionatlity as rproc_fw_boot(), but without the steps that
involve interaction with the firmware image.  That way we can
deal with scenarios where the remoteproc core is attaching
to a remote processor that has already been started by another
entity.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Tested-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Link: https://lore.kernel.org/r/20200714195035.1426873-5-mathieu.poirier@linaro.org


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