ARM: dts: imx7d-mba7: Remove unsupported PCI properties

disable-gpio' and 'power-on-gpio' are not valid properties
according to Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt.

Remove the unsupported properties.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Bruno Thomsen <bruno.thomsen@gmail.com>
Reviewed-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>