This patch change the align of mbox stack resource to 32. The reason is
that I had some experience with bcm2836 and the mbox implementation,
after setting the align to 64(on bcm2836) the issues was gone.

I found these values inside the u-boot implementation, they use 32
(bcm2835) and 64 (bcm2836).

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>