chane TRX0/TS0 channel combination to not include a CBCH

We don't support CBCH anyway, and using CBCH will reduce the number of uesable
SDCCH/4 channels to 3 on TS0
diff --git a/openbsc/src/chan_alloc.c b/openbsc/src/chan_alloc.c
index 860355a..5d1e137 100644
--- a/openbsc/src/chan_alloc.c
+++ b/openbsc/src/chan_alloc.c
@@ -80,13 +80,11 @@
 			case GSM_PCHAN_CCCH_SDCCH4:
 				from = 0; to = 0;
 				break;
-			case GSM_PCHAN_SDCCH8_SACCH8C:
-				from = 1; to = 1;
-				break;
 			case GSM_PCHAN_TCH_F:
 			case GSM_PCHAN_TCH_H:
-				from = 2; to = 7;
+				from = 1; to = 7;
 				break;
+			case GSM_PCHAN_SDCCH8_SACCH8C:
 			default:
 				return NULL;
 			}
@@ -94,9 +92,11 @@
 			/* Every secondary TRX is configured for TCH/F
 			 * and TCH/H only */
 			switch (pchan) {
+			case GSM_PCHAN_SDCCH8_SACCH8C:
+				from = 1; to = 1;
 			case GSM_PCHAN_TCH_F:
 			case GSM_PCHAN_TCH_H:
-				from = 0; to = 7;
+				from = 1; to = 7;
 				break;
 			default:
 				return NULL;