libahci_platform: Fail when PHY required but PHY support disabled

ahci_platform_get_resources handles resource management for
platform AHCI drivers, including getting a possible PHY
from the device tree. Since not all drivers need a PHY, it
ignores -ENODEV and -ENOSYS from devm_get_phy. However, when
the PHY subsystem is mistakenly disabled, -ENOSYS can be
returned even when a PHY is needed.

This patch modifies the -ENOSYS case to check if a "phys"
device tree node exists. If it exists, then clearly the PHY
subsystem is mistakenly disabled and the driver cannot work,
ahci_platform_get_resources will fail and propagate the error.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Tejun Heo <tj@kernel.org>