dt-bindings: gpio: Add pmc gpio node to gpio-zynq

Add the pmc gpio node to the device tree.

Versal devices are the industry's first adaptive compute
acceleration platforms.
https://www.xilinx.com/support/documentation/data_sheets/ds950-versal-overview.pdf

On the Versal platform, we are using two customized GPIO controllers(IP)
which were used in Zynq/ZynqMp platform.
One of them present in the Platform Management Controller(PMC) block and
other in Processing System(PS) block.

In PMC_GPIO only Bank0,1,3 & 4 are enabled and in PS_GPIO only
Bank 0 & 3 are enabled.

You can find more details of GPIO IP in ZynqMP TRM General Purpose
I/O(Chapter-27).
https://www.xilinx.com/support/documentation/user_guides/ug1085-zynq-ultrascale-trm.pdfSigned-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Documentation/devicetree/bindings/gpio/gpio-zynq.txt

@@ -8,6 +8,7 @@ Required properties:
 			    parameters (unused)
 - compatible		: Should be "xlnx,zynq-gpio-1.0" or
 			  "xlnx,zynqmp-gpio-1.0" or "xlnx,versal-gpio-1.0
+			  or "xlnx,pmc-gpio-1.0
 - clocks		: Clock specifier (see clock bindings for details)
 - gpio-controller	: Marks the device node as a GPIO controller.
 - interrupts		: Interrupt specifier (see interrupt bindings for