soc: qcom: smd: Split discovery and state change work

Split the two steps of channel discovery and state change handling into
two different workers. This allows for new channels to be found while
we're are probing, which is required as we introduce multi-channel
support.

Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>