cbfs: Simplify file iteration

In file_cbfs_next_file() there is a lot of complicated code to move to
the next file. Use the ALIGN() macros to simplify this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/fs/cbfs/cbfs.c b/fs/cbfs/cbfs.c
index a93dc3d..9e534d1 100644
--- a/fs/cbfs/cbfs.c
+++ b/fs/cbfs/cbfs.c
@@ -133,7 +133,6 @@
 
 	while (size >= align) {
 		const struct cbfs_fileheader *file_header = start;
-		u32 step;
 		int ret;
 
 		/* Check if there's a file here. */
@@ -152,11 +151,7 @@
 			return log_msg_ret("fill", ret);
 		}
 
-		step = header.len;
-		if (step % align)
-			step = step + align - step % align;
-
-		*used += step;
+		*used += ALIGN(header.len, align);
 		return 0;
 	}