scoutfs: add SIC_EXACT

Add an item count call that lets the caller give the exact item count
instead of basing it on the operation they're performing.

Signed-off-by: Zach Brown <zab@versity.com>

kmod/src/count.h

@@ -22,6 +22,18 @@ struct scoutfs_item_count {
 	signed vals;
 };
 
+/* The caller knows exactly what they're doing. */
+static inline const struct scoutfs_item_count SIC_EXACT(signed items,
+							signed vals)
+{
+	struct scoutfs_item_count cnt = {
+		.items = items,
+		.vals = vals,
+	};
+
+	return cnt;
+}
+
 /*
  * Allocating an inode creates a new set of indexed items.
  */