qcom-smd: Restructure device model and support more smd functionality

Add support for multiple devices per edge and support each device have multiple
channels. Probe these when the channels become available, triggered by
interrupt on each edge.

Also add support for byte-aligned channel control structures, so that we can
communicate with e.g. wcnss.

Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>