soundwire: Add dependency on WCD934X codec for slave

WCD934x codecs have soundwire master controller and can
connect to devices with soundwire slave. Hence, add a
dependency on WCD934x codec, so that the slave code can
be selected for compilation.

Change-Id: Ied3288a330b96205c253c641a2a73df35a7355fb
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>