PCI: rockchip: Fix legacy IRQ generation for RK3399 PCIe endpoint core

commit 166e89d99dd85a856343cca51eee781b793801f2 upstream.

Fix legacy IRQ generation for RK3399 PCIe endpoint core according to
the technical reference manual (TRM). Assert and deassert legacy
interrupt (INTx) through the legacy interrupt control register
("PCIE_CLIENT_LEGACY_INT_CTRL") instead of manually generating a PCIe
message. The generation of the legacy interrupt was tested and validated
with the PCIe endpoint test driver.

Link: https://lore.kernel.org/r/20230418074700.1083505-8-rick.wertenbroek@gmail.com


Fixes: cf590b07 ("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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>