ONFI parameters are little-endian, hence we must take care to convert them
to native endianness.  We must also pay attention to unaligned accesses.

Copy the interesting parameters to a new struct so the rest of the code can
forget about these problems.

Submitted by:	Kristof Provost <kristof@sigsegv.be> (cleanup) and me (orig).
Move the luns field to the end of the struct, for serendipitous packing.
(I was supposed to do this before committing it initially.)
Rework the routine that returns a pointer to the table of software ECC
byte positions within the OOB area to support chips with unusual OOB
sizes such as 218 or 224 bytes.

The table for 128 byte OOB works for these but it assumes 3 bytes of ECC
per 256 byte block, and in the case of an ONFI chip the params page may
ask for something different.  In other words, this is better but not
yet perfect.