GPU: State: Add GPU_BARRIER_UNIFORM

This allows to synchronise uniform buffer writes from compute shader
when an UBO is bound as SSBO.

source/blender/gpu/opengl/gl_state.hh

@@ -130,6 +130,9 @@ static inline GLbitfield to_gl(eGPUBarrier barrier_bits)
   if (barrier_bits & GPU_BARRIER_ELEMENT_ARRAY) {
     barrier |= GL_ELEMENT_ARRAY_BARRIER_BIT;
   }
+  if (barrier_bits & GPU_BARRIER_UNIFORM) {
+    barrier |= GL_UNIFORM_BARRIER_BIT;
+  }
   return barrier;
 }