ata: libahci_platform: use flex array for platform PHYs

ata: libahci_platform: use flex array for platform PHYs

Modify struct ahci_host_priv to use a flexible array member for an adapter
port PHYs and use struct_size to combine the allocation of this array
together with the adapter private data structure. __counted_by() annotation
is added for the phys field to support runtime analysis.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Niklas Cassel <cassel@kernel.org>