devicetree: bindings: hisi_sas: add v2 HW bindings

Add the dt bindings for HiSi SAS controller v2 HW.

The main difference in the controller from dt perspective is
interrupts. The v2 controller does not have dedicated fatal and
broadcast interrupts - they are multiplexed on the channel interrupt.

Each SAS v2 controller can issue upto 64 commands (or connection
requests) on the system bus without waiting for a response - this is
know as am-max-transmissions.  In hip06, sas controller #1 has a
limitation that it has to limit am-max-transmissions to 32 - this
limitation is due to chip system bus design. It is not anticipated that
any future chip incorporating v2 controller will have such a limitation.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>