bts: Arfcn can never be smaller than 0

Remove the condition because it can never be true.

Fixes: Coverity CID#1307793
diff --git a/openbsc/src/libbsc/bsc_init.c b/openbsc/src/libbsc/bsc_init.c
index a63528c..46d95cc 100644
--- a/openbsc/src/libbsc/bsc_init.c
+++ b/openbsc/src/libbsc/bsc_init.c
@@ -397,8 +397,7 @@
 		}
 		break;
 	case GSM_BAND_900:
-		if (bts->c0->arfcn < 0 ||
-		   (bts->c0->arfcn > 124 && bts->c0->arfcn < 955) ||
+		if ((bts->c0->arfcn > 124 && bts->c0->arfcn < 955) ||
 		    bts->c0->arfcn > 1023)  {
 			LOGP(DNM, LOGL_ERROR, "GSM900 channel must be between 0-124, 955-1023.\n");
 			return -EINVAL;