dt-bindings: PCI: fsl,imx6q-pcie: Add missing type for 'reset-gpio-active-high'

'reset-gpio-active-high' is missing a type definition and is not a common
property. The type is boolean.

Signed-off-by: Rob Herring <[e-mail]>
Acked-by: Richard Zhu <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml

···
     description: If present then the reset sequence using the GPIO
       specified in the "reset-gpio" property is reversed (H=reset state,
       L=operation state) (optional required).
+    type: boolean
 
   vpcie-supply:
     description: Should specify the regulator in charge of PCIe port power.