Enable creating and assembling raid5 arrays with PPL for 1.x metadata.
When creating, reserve enough space for PPL and store its size and
location in the superblock and set MD_FEATURE_PPL bit. Write an initial
empty header in the PPL area on each device. PPL is stored in the
metadata region reserved for internal write-intent bitmap, so don't
allow using bitmap and PPL together.
While at it, fix two endianness issues in write_empty_r5l_meta_block()
and write_init_super1().
Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com> Signed-off-by: Jes Sorensen <Jes.Sorensen@gmail.com>