dt-bindings: ata: sata: Extend number of SATA ports

The denoted in the description upper limit only concerns the Port
Multipliers, but not the actual SATA ports. It's an external device
attached to a SATA port in order to access more than one SATA-drive. So
when it's attached to a SATA port it just extends the port capability
while the number of actual SATA ports stays the same. For instance on AHCI
controllers the number of actual ports is determined by the CAP.NP field
and the PI (Ports Implemented) register. AFAICS in general the maximum
number of SATA ports depends on the particular controller implementation.
Generic AHCI controller can't have more than 32 ports (since CAP.NP is of
5 bits wide and PI register is 32-bits size), while DWC AHCI SATA
controller can't be configured with more than 8 ports activated. So let's
discard the SATA ports reg-property restrictions and just make sure that
it consists of a single reg-item.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>