remoteproc: Introduce custom dump function for each remoteproc segment

Introduce custom dump function and private data per remoteproc dump
segment. The dump function is responsible for filling the device memory
segment associated with coredump

Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>