EEVEE-Next: Fix shader compilation error.

This fixes a compilation error in eevee_light_culling_debug shader.

Some compilers complained when accessing the same data twice. Unclear
why. We should investigate that this change doesn't harm the performance
of the shader.

Although the light is a local variable it might clutter available
registers. If so it will harm developers during debugging.

source/blender/draw/engines/eevee_next/shaders/eevee_light_culling_debug_frag.glsl

@@ -36,7 +36,7 @@ void main()
     vec3 L;
     float dist;
     light_vector_get(light, P, L, dist);
-    if (light_attenuation(light_buf[l_idx], L, dist) > 0.0) {
+    if (light_attenuation(light, L, dist) > 0.0) {
       light_nocull |= 1u << l_idx;
     }
   }