ore: Enable RAID5 mounts

Now that we support raid5 Enable it at mount. Raid6 will come next
raid4 is not demanded for so it will probably not be enabled.
(Until some one wants it)

NOTE: That mkfs.exofs had support for raid5/6 since long time
ago. (Making an empty raidX FS is just as easy as raid0 ;-} )

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>