Btrfs: remove warn on in free space cache writeout

This catches block groups that are too large to properly cache.  We deal with
this case fine, so the warning just confuses users.  Remove the warning.
Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index ecca6c7..6a8bb9c 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -920,10 +920,8 @@
 
 	/* Make sure we can fit our crcs into the first page */
 	if (io_ctl.check_crcs &&
-	    (io_ctl.num_pages * sizeof(u32)) >= PAGE_CACHE_SIZE) {
-		WARN_ON(1);
+	    (io_ctl.num_pages * sizeof(u32)) >= PAGE_CACHE_SIZE)
 		goto out_nospc;
-	}
 
 	io_ctl_set_generation(&io_ctl, trans->transid);