remoteproc: qcom: Introduce helper to store pil info in IMEM

A region in IMEM is used to communicate load addresses of remoteproc to
post mortem debug tools. Implement a helper function that can be used to
store this information in order to enable these tools to process
collected ramdumps.

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20200622191942.255460-3-bjorn.andersson@linaro.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>