pata_legacy: Properly document module parameters

Most pata_legacy module parameters lack MODULE_PARM_DESC documentation
and none is described in kernel-parameters.txt.  Also several comments
are inaccurate or wrong.

Add the missing documentation pieces then and reorder parameters into a
consistent block.  Remove inaccuracies as follows:

- `all' affects primary and secondary port ranges only rather than all,

- `probe_all' affects tertiary and further port ranges rather than all,

- `ht6560b' is for HT 6560B rather than HT 6560A.

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/alpine.DEB.2.21.2103211909560.21463@angie.orcam.me.uk


Signed-off-by: Jens Axboe <axboe@kernel.dk>