tools: move alignment-related macros to new <linux/align.h>

Currently, tools have *ALIGN*() macros scattered across the unrelated
headers, as there are only 3 of them and they were added separately
each time on an as-needed basis.
Anyway, let's make it more consistent with the kernel headers and allow
using those macros outside of the mentioned headers. Create
<linux/align.h> inside the tools/ folder and include it where needed.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>