soundwire: put soundwire in suspend state when system is idle

Put soundwire in suspend state when system is in idle state.
This will avoid power consumption on speakers when system is in
idle state.

Change-Id: I4f38457fa7681957e21ff1381f9bd841533bd7b5
Signed-off-by: Sudheer Papothi <spapothi@codeaurora.org>