asoc: Add control to set AFE Tx loopback port

AFE TX loopback is used to capture playback data from RX port
and use it for echo reference. Add new control to configure
Rx port to read data from in this case. Existing control was
re-using EC Ref rx port control and can lead to far end
configuration in undesired cases. Extend existing
MultiMedia1 Output Channel control to support 10channels.

Change-Id: I98f11d315e97d761ac2c8f8bf3ef387568c85082
Signed-off-by: Chaithanya Krishna Bacharaju <chaithan@codeaurora.org>