Fix the reported status for the switch CPU port which was (wrongly)
reporting half-duplex link.

Tested on TP-Link WR1043ND.
Actually pro AMD chipsets.

MFC after:	3 days
Sponsored by:	Bally Wulff Games & Entertainment GmbH
Add more formal and strict command parsing and validation.

For every supported command define CDB length and mask of bits that are
allowed to be set.  This allows to remove bunch of checks through the code
and still make the validation more strict.  To properly do it for commands
supporting multiple service actions, formalize their parsing by adding
subtables for each of such commands.

As visible effect, this change allows to add support for REPORT SUPPORTED
OPERATION CODES command, reporting to client all the data about supported
SCSI commands, except timeouts.

MFC after:	2 weeks