remoteproc: Modify recovery path to use rproc_{start,stop}()

Replace rproc_shutdown() by rproc_stop() and rproc_boot() by
rproc_start() in the recovery path, in order to avoid remoteproc
resources re-allocation overhead and to assist with extracting the
coredumps after stopping the remote processor.

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