wpan: fix build issues

- Remove refernce to non existent files in ti-wpan-products.mk
- Include wpan components only for TI builds

Signed-off-by: Vishal Mahaveer <vishalm@ti.com>
Signed-off-by: Michael Bestas <mikeioannina@gmail.com>

Change-Id: Id731c538f814ff9ab296c0bae19deaf58ed03b7e