pci: renesas: Add root bus handling on Gen3

Add code to access the PCIe root bus space and configure it.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Bin Meng <bmeng.cn@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
1 file changed