tools: kwbimage: Align BIN header executable code to 128-bit boundary

ARM executable code inside the BIN header on some mvebu platforms
(e.g. A370, AXP) must always be aligned with the 128-bit boundary. This
requirement can be met by inserting dummy arguments into BIN header.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>