bootutil: Enable hash calculation directly on storage

The commit add support for passing storage device address space
to hash calculation functions, which allows to use hardware
accelerated hash calculation on storage.
This feature only works when image encryption is not enabled
and all slots are defined within internal storage of device.

The feature is enabled with MCUboot configuration option
MCUBOOT_HASH_STORAGE_DIRECTLY.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>