PCI: rockchip: Make some regulators non-optional

The 0V9 and 1V8 supplies power the PCIe block in the SoC itself, and
are thus fundamental to PCIe being usable at all. As such, it makes
sense to treat them as non-optional and rely on dummy regulators if
not explicitly described.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Andrew Murray <andrew.murray@arm.com>