reset: uniphier: add PCIe reset control support

Add reset lines for PCIe controller on UniPhier SoCs. This adds support for
Pro5, LD20 and PXs3.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>