remoteproc: Introduce rproc_{start,stop}() functions

remoteproc: Introduce rproc_{start,stop}() functions

In the context of recovering from crash, rproc_trigger_recovery() does
rproc_shutdown() followed by rproc_boot(). The remoteproc resources are
cleaned up in rproc_shutdown() and immediately reallocated in
rproc_boot() which is an unnecessary overhead. Furthermore, we want the
memory regions to be accessible after stopping the remote processor, to
be able to extract the memory content for a coredump.

This patch factors out the code in rproc_boot() and rproc_shutdown()
path and introduces rproc_{start,stop}() in order to avoid resource
allocation overhead.

Signed-off-by: Sarangdhar Joshi <spjoshi@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>