soundwire: Replace 'objs' by 'y'

`-objs` is designed for building host programs, change to `-y`,
more straightforward for device drivers.

See Documentation/kbuild/makefiles.rst

Signed-off-by: Vinod Koul <vkoul@kernel.org>
Link: https://lore.kernel.org/r/20200616162140.2563535-1-vkoul@kernel.org


Signed-off-by: Vinod Koul <vkoul@kernel.org>