ARM: imx6: correct i.MX6 PCIe interrupt routing

commit 1a9fa190956f45c1e58c4d8bfa5ac051691ea590 upstream.

The PCIe interrupts are also routed through the GPC. This has been
missed from the conversion to stacked IRQ domains as the PCIe
controller uses an explicit interrupt map and thus doesn't inherit
the SoC global interrupt parent.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

(cherry picked from commit cdda95937ec1f62e29f6e89c87600555594f3dec)
Signed-off-by: Alex Shi <alex.shi@linaro.org>