remoteproc: Move coredump functionality to a new file

Move all coredump functionality to an individual file. This is
being done so that the current functionality can be extended
in future patchsets.

Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Sibi Sankar <sibis@codeaurora.org>
Tested-by: Sibi Sankar <sibis@codeaurora.org>
Link: https://lore.kernel.org/r/1594938035-7327-2-git-send-email-rishabhb@codeaurora.org


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