The Oren Nayer diffuse BSDF had a energy compensation term added in a
recent commit[1]. This energy compensation term used the colour input
in it's computation. The colour input was clamped in SVM, but not OSL,
resulting in differences between the two backends. This commit resolves
this issue by clamping the colour in the OSL script to match SVM.
[1] 5e40b9bb5c
Pull Request: https://projects.blender.org/blender/blender/pulls/123527
89583e991d