PCI: kirin: Use regmap for APB registers

The PHY layer need to access APB registers too, for Kirin 970.  So place
them into a named regmap.

Link: https://lore.kernel.org/r/daf0e4bda5a69a5ac8484e70f09351a959805c8c.1634812676.git.mchehab+huawei@kernel.org


Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Xiaowei Song <songxiaowei@hisilicon.com>