common: add a macro to align an array on the stack
The macro can be used for temporary stack buffers which need to meet
a minimum alignment requirement.
This will be used by bcm2835 mailbox users, where all buffers need to
be aligned.
Signed-off-by: Andre Heider <a.heider@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>