dt-bindings: firmware: xilinx: Fix versal-fpga node name

Based on commit 83a368a3fc ("docs: dt-bindings: add DTS Coding Style
document") using underscore ('_') in node name is not recommended that's
why switch to dash ('-').

Acked-by: Xu Yilun <yilun.xu@intel.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/6779af2f9cc21c912f10cf310388d99b980800b2.1702996281.git.michal.simek@amd.com
Signed-off-by: Michal Simek <michal.simek@amd.com>

Documentation/devicetree/bindings/firmware/xilinx/xlnx,zynqmp-firmware.yaml

@@ -47,7 +47,7 @@ properties:
   "#power-domain-cells":
     const: 1
 
-  versal_fpga:
+  versal-fpga:
     $ref: /schemas/fpga/xlnx,versal-fpga.yaml#
     description: Compatible of the FPGA device.
     type: object
@@ -90,7 +90,7 @@ examples:
       compatible = "xlnx,versal-firmware";
       method = "smc";
 
-      versal_fpga: versal_fpga {
+      versal_fpga: versal-fpga {
         compatible = "xlnx,versal-fpga";
       };
 

Documentation/devicetree/bindings/fpga/xlnx,versal-fpga.yaml

@@ -26,7 +26,7 @@ additionalProperties: false
 
 examples:
   - |
-    versal_fpga: versal_fpga {
+    versal_fpga: versal-fpga {
          compatible = "xlnx,versal-fpga";
     };