tbf: Warn about copy and paste between different tbf alloc routines

These need to be re-factored to use a common allocation routine.
diff --git a/src/tbf.cpp b/src/tbf.cpp
index 8dad6bc..21b58ac 100644
--- a/src/tbf.cpp
+++ b/src/tbf.cpp
@@ -141,6 +141,7 @@
 	}
 
 	// Create new TBF (any TRX)
+#warning "Copy and paste with alloc_ul_tbf"
 	tfi = tfi_find_free(bts, GPRS_RLCMAC_DL_TBF, &trx, use_trx);
 	if (tfi < 0) {
 		LOGP(DRLCMAC, LOGL_NOTICE, "No PDCH resource\n");