soundwire: set the group id based on number of channels

Set the group id to default when number of channels are less
than or equal to one. This change will configure the group
id correctly during device switch scenarios.

CRs-Fixed: 961023
Change-Id: I2cb4447b36fef111ed1f9b8991b3882b8d57f6a7
Signed-off-by: Sudheer Papothi <spapothi@codeaurora.org>