dt-bindings: interrupt-controller: Add arm,armv7m-nvic and fix #interrupt-cells

According to existed dts arch/arm/boot/dts/armv7-m.dtsi and driver
drivers/irqchip/irq-nvic.c, compatible string should be arm,armv7m-nvic,

Fix below CHECK_DTB warning:

arch/arm/boot/dts/nxp/vf/vf610m4-cosmic.dtb: /interrupt-controller@e000e100:
    failed to match any schema with compatible: ['arm,armv7m-nvic']

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20250624224630.2518776-1-Frank.Li@nxp.com
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>

Documentation/devicetree/bindings/interrupt-controller/arm,nvic.yaml

@@ -17,6 +17,7 @@ description:
 properties:
   compatible:
     enum:
+      - arm,armv7m-nvic # deprecated
       - arm,v6m-nvic
       - arm,v7m-nvic
       - arm,v8m-nvic
@@ -30,7 +31,7 @@ properties:
   interrupt-controller: true
 
   '#interrupt-cells':
-    const: 2
+    enum: [1, 2]
     description: |
       Number of cells to encode an interrupt source:
       first = interrupt number, second = priority.