PCI: rockchip: Assert PCI Configuration Enable bit after probe

PCI: rockchip: Assert PCI Configuration Enable bit after probe

Assert PCI Configuration Enable bit after probe. When this bit is left to
0 in the endpoint mode, the RK3399 PCIe endpoint core will generate
configuration request retry status (CRS) messages back to the root complex.
Assert this bit after probe to allow the RK3399 PCIe endpoint core to reply
to configuration requests from the root complex.
This is documented in section 17.5.8.1.2 of the RK3399 TRM.

Link: https://lore.kernel.org/r/20230418074700.1083505-4-rick.wertenbroek@gmail.com
Fixes: cf590b078391 ("PCI: rockchip: Add EP driver for Rockchip PCIe controller")
Tested-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Rick Wertenbroek <rick.wertenbroek@gmail.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Cc: stable@vger.kernel.org