ata: ahci: mvebu: Make SATA PHY optional for Armada 3720

Older ATF does not provide SMC call for SATA phy power on functionality and
therefore initialization of ahci_mvebu is failing when older version of ATF
is using. In this case phy_power_on() function returns -EOPNOTSUPP.

This patch adds a new hflag AHCI_HFLAG_IGN_NOTSUPP_POWER_ON which cause
that ahci_platform_enable_phys() would ignore -EOPNOTSUPP errors from
phy_power_on() call.

It fixes initialization of ahci_mvebu on Espressobin boards where is older
Marvell's Arm Trusted Firmware without SMC call for SATA phy power.

This is regression introduced in commit 8e18c8e58da64 ("arm64: dts: marvell:
armada-3720-espressobin: declare SATA PHY property") where SATA phy was
defined and therefore ahci_platform_enable_phys() on Espressobin started
failing.

Fixes: 8e18c8e58da64 ("arm64: dts: marvell: armada-3720-espressobin: declare SATA PHY property")
Signed-off-by: Pali Rohár <pali@kernel.org>
Tested-by: Tomasz Maciej Nowak <tmn505@gmail.com>
Cc: <stable@vger.kernel.org> # 5.1+: ea17a0f153af: phy: marvell: comphy: Convert internal SMCC firmware return codes to errno
Signed-off-by: Jens Axboe <axboe@kernel.dk>