remoteproc: stm32: Move memory parsing to rproc_ops

remoteproc: stm32: Move memory parsing to rproc_ops

Some actions such as memory resources reallocation are needed when
trying to reattach a co-processor. Use the prepare() operation for
these actions.

Co-developed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Arnaud POULIQUEN <arnaud.pouliquen@foss.st.com>
Link: https://lore.kernel.org/r/20210312162453.1234145-8-mathieu.poirier@linaro.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>