kwbimage: Align payload size to 4 bytes

The MVEBU BootROM does not allow non word aligned payloads.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Luka Perkov <luka.perkov@sartura.hr>
diff --git a/tools/kwbimage.c b/tools/kwbimage.c
index 5e62d08..d33f1b6 100644
--- a/tools/kwbimage.c
+++ b/tools/kwbimage.c
@@ -681,6 +681,9 @@
 		exit(EXIT_FAILURE);
 	}
 
+	/* The MVEBU BootROM does not allow non word aligned payloads */
+	sbuf->st_size = ALIGN_SUP(sbuf->st_size, 4);
+
 	version = image_get_version();
 	switch (version) {
 		/*