glsl: exit loop early if we find xfb layout qualifers

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>

src/compiler/glsl/link_varyings.cpp

@@ -120,6 +120,7 @@ process_xfb_layout_qualifiers(void *mem_ctx, const gl_linked_shader *sh,
    for (unsigned j = 0; j < MAX_FEEDBACK_BUFFERS; j++) {
       if (sh->info.TransformFeedback.BufferStride[j]) {
          has_xfb_qualifiers = true;
+         break;
       }
    }