dt-binding: remoteproc: Introduce Qualcomm WCNSS loader binding

The document defines the binding for a component that loads firmware for
and boots the Qualcomm WCNSS core.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>