[lchan] Fix the SAPI reset in the chan allocation...

Reset the whole array instead of just the first element.
diff --git a/openbsc/src/chan_alloc.c b/openbsc/src/chan_alloc.c
index 7464aa9..bd3ec85 100644
--- a/openbsc/src/chan_alloc.c
+++ b/openbsc/src/chan_alloc.c
@@ -213,7 +213,7 @@
 		lchan->use_count = 0;
 
 		/* clear sapis */
-		memset(lchan->sapis, 0, sizeof(lchan->sapis));
+		memset(lchan->sapis, 0, ARRAY_SIZE(lchan->sapis));
 
 		/* Configure the time and start it so it will be closed */
 		lchan->release_timer.cb = auto_release_channel;