PCI: rockchip: Use pci_host_probe() to register host

PCI: rockchip: Use pci_host_probe() to register host

The rockchip host driver does the same host registration and bus scanning
calls as pci_host_probe, so let's use it instead.

Link: https://lore.kernel.org/r/20200522234832.954484-14-robh@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Shawn Lin <shawn.lin@rock-chips.com>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: linux-rockchip@lists.infradead.org