gvfs: Handle samba dependency based on GPLv3 license.

* Samba is GPLv3. In GPLv3 free environment one was not able to
  build gvfs. Add PACKAGECONFIG for samba and enable is when GPLv3
  is not present in INCOMPATIBLE_LICENSE.

Signed-off-by: Noor Ahsan <noor_ahsan@mentor.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>