soc: qcom: Remote filesystem memory driver

The Qualcomm remote file system protocol is used by certain remoteprocs,
in particular the modem, to read and write persistent storage in
platforms where only the application CPU has physical storage access.

The protocol is based on a set of QMI-encoded control-messages and a
shared memory buffer for exchaning the data. This driver implements the
latter, providing the user space service access to the carved out chunk
of memory.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>