arm: Add HOLES_IN_ZONE option

Previous, commit 14e07298
(add pfn_valid_within helper for sub-MAX_ORDER hole detection)
added support for the HOLES_IN_ZONE option. A corresponding
Kconfig was added to ia64 but not arm. Add support for this
option.

Change-Id: Ia37263f0f448cdbceb37ac2525cca906ba53f0f8
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
(cherry picked from commit 224d00ca68501bea52600e53c12a37f7ef96172d)