Modularize, cleanup, add comments - for FDMI code in driver

Note: I don't like the comments with leading # - but as we have a lot if
present, I'm deferring to handle it in one big fix later.
Signed-off-by: NDick Kennedy <dick.kennedy@avagotech.com>
Signed-off-by: NJames Smart <james.smart@avagotech.com>
Reviewed-by: NHannes Reinicke <hare@suse.de>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>