Revert "Fix scenegraph backend API for material shaders."

This reverts commit a8a90519cb35481e96fe8889846bfaa424e13e8a. The
same functionality is now available in a more extensible way via
the program binary support recently added.

Change-Id: I07b1939611a76858e65605ce625da6c4cbca2114
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>