tgsi: also dump label for TGSI_OPCODE_BGNSUB opcode

So we can see the label associated with subroutines.

Reviewed-by: José Fonseca <jfonseca@vmware.com>

src/gallium/auxiliary/tgsi/tgsi_dump.c

@@ -606,6 +606,7 @@ iter_instruction(
    case TGSI_OPCODE_BGNLOOP:
    case TGSI_OPCODE_ENDLOOP:
    case TGSI_OPCODE_CAL:
+   case TGSI_OPCODE_BGNSUB:
       TXT( " :" );
       UID( inst->Label.Label );
       break;