Blender Git Loki

Code cleanup: remove parameter from GPU_node_link_create()

In all but one call the value 0 (aka GPU_NONE) was passed in. Clearer
to just default to GPU_NONE and change the one caller that sets a real
type to do it explicitly.

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D1026