ata: libahci_platform: comply to PHY framework

Current implementation of the libahci does not take into account the
new PHY framework. Correct the situation by adding a call to
phy_set_mode() before phy_power_on().

PHYs should also be handled at suspend/resume time. For this, call
ahci_platform_enable/disable_phys() at suspend/resume_host() time. These
calls are guarded by a HFLAG (AHCI_HFLAG_SUSPEND_PHYS) that the user of
the libahci driver must set manually in hpriv->flags at probe time. This
is to avoid breaking users that have not been tested with this change.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Suggested-by: Grzegorz Jaszczyk <jaz@semihalf.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>