ata: libahci: allow to use multiple PHYs

The current implementation of the libahci does not allow to use multiple
PHYs. This patch adds the support of multiple PHYs by the libahci while
keeping the old bindings valid for device tree compatibility.

This introduce a new way of defining SATA ports in the device tree, with
one port per sub-node. This as the advantage of allowing a per port
configuration. Because some ports may be accessible but disabled in the
device tree, the port_map mask is computed automatically when using
this.

Signed-off-by: Antoine Ténart <antoine.tenart@free-electrons.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Tejun Heo <tj@kernel.org>