in_pin and out_pin list for a module has the information about
the module that are bound together. So we can directly look at
pin information of module for binding and unbind.

As a result the preinitialized dapm_path_last we had is removed
and code and memory optimzed.
Signed-off-by: Jeeja KP <jeeja.kp@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>