arm: Add app data section alignment constraints

This patch adds application data section alignment constraints
to match the region definition requirements for ARM MPUs.  Most MPUs
require a minimum of 32 bytes of alignment for any regions, but some
require power of two alignment to the size of a region.

This requires that the linker align the application data section to
the size of the section.  This requires a linker pass to determine the
size.  Once this is accomplished the correct value is added to a linker
include file that is utilized in subsequent linker operations.

Signed-off-by: Andy Gross <andy.gross@linaro.org>