Fix for recent changes in glsl

smooth seems to be a keyword in glsl and using it as a name for function property caused issues.

source/blender/gpu/shaders/gpu_shader_material.glsl

@@ -2188,7 +2188,7 @@ void node_light_path(
 	is_transmission_ray = 0.0;
 }
 
-void node_light_falloff(float strength, float smooth, out float quadratic, out float linear, out float constant)
+void node_light_falloff(float strength, float tsmooth, out float quadratic, out float linear, out float constant)
 {
 	quadratic = strength;
 	linear = strength;