ata: libahci_platform: Fix regulator_get_optional() misuse

This driver is using regulator_get_optional() to handle all the supplies
that it handles, and only ever enables and disables all supplies en masse
without ever doing any other configuration of the device to handle missing
power. These are clear signs that the API is being misused - it should only
be used for supplies that may be physically absent from the system and in
these cases the hardware usually needs different configuration if the
supply is missing. Instead use normal regualtor_get(), if the supply is
not described in DT then the framework will substitute a dummy regulator in
so no special handling is needed by the consumer driver.

In the case of the PHY regulator the handling in the driver is a hack to
deal with integrated PHYs; the supplies are only optional in the sense
that that there's some confusion in the code about where they're bound to.
From a code point of view they function exactly as normal supplies so can
be treated as such. It'd probably be better to model this by instantiating
a PHY object for integrated PHYs.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>