i965: be clear that the Fallback field is a boolean, not a bitfield

src/mesa/drivers/dri/i965/brw_draw_upload.c

@@ -375,7 +375,7 @@ static void brw_prepare_vertices(struct brw_context *brw)
     * isn't an issue at this point.
     */
    if (brw->vb.nr_enabled >= BRW_VEP_MAX) {
-      intel->Fallback = 1;
+      intel->Fallback = GL_TRUE; /* boolean, not bitfield */
       return;
    }
 
@@ -427,7 +427,7 @@ static void brw_prepare_vertices(struct brw_context *brw)
 	    /* Position array not properly enabled:
 	     */
             if (input->glarray->StrideB == 0) {
-               intel->Fallback = 1;
+               intel->Fallback = GL_TRUE; /* boolean, not bitfield */
                return;
             }
 

src/mesa/drivers/dri/i965/brw_fallback.c

@@ -133,7 +133,11 @@ const struct brw_tracked_state brw_check_fallback = {
 
 
 
-/* Not used:
+/**
+ * Called by the INTEL_FALLBACK() macro.
+ * NOTE: this is a no-op for the i965 driver.  The brw->intel.Fallback
+ * field is treated as a boolean, not a bitmask.  It's only set in a
+ * couple of places.
  */
 void intelFallback( struct intel_context *intel, GLuint bit, GLboolean mode )
 {

src/mesa/drivers/dri/i965/brw_state_upload.c

@@ -308,7 +308,7 @@ void brw_validate_state( struct brw_context *brw )
    if (brw->state.dirty.brw & BRW_NEW_CONTEXT)
       brw_clear_batch_cache(brw);
 
-   brw->intel.Fallback = 0;
+   brw->intel.Fallback = GL_FALSE; /* boolean, not bitfield */
 
    /* do prepare stage for all atoms */
    for (i = 0; i < Elements(atoms); i++) {