dt-bindings: interrupt-controller: Convert al,alpine-msix to DT schema

Convert the Amazaon Alpine MSIX controller binding to schema format.

Drop the interrupt-controller property as the MSIX controller doesn't
provide interrupts. The interrupt-parent property is required in this
case for custom MSI mapping properties.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Rob Herring (Arm) <[e-mail]>

Documentation/devicetree/bindings/interrupt-controller/al,alpine-msix.txt

···
-Alpine MSIX controller
-
-See arm,gic-v3.txt for SPI and MSI definitions.
-
-Required properties:
-
-- compatible: should be "al,alpine-msix"
-- reg: physical base address and size of the registers
-- interrupt-controller: identifies the node as an interrupt controller
-- msi-controller: identifies the node as an PCI Message Signaled Interrupt
-		  controller
-- al,msi-base-spi: SPI base of the MSI frame
-- al,msi-num-spis: number of SPIs assigned to the MSI frame, relative to SPI0
-
-Example:
-
-msix: msix {
-	compatible = "al,alpine-msix";
-	reg = <0x0 0xfbe00000 0x0 0x100000>;
-	interrupt-parent = <&gic>;
-	interrupt-controller;
-	msi-controller;
-	al,msi-base-spi = <160>;
-	al,msi-num-spis = <160>;
-};

Documentation/devicetree/bindings/interrupt-controller/al,alpine-msix.yaml

···
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/interrupt-controller/al,alpine-msix.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Alpine MSIX controller
+
+maintainers:
+  - Antoine Tenart <[e-mail]>
+
+properties:
+  compatible:
+    const: al,alpine-msix
+
+  reg:
+    maxItems: 1
+
+  interrupt-parent: true
+
+  msi-controller: true
+
+  al,msi-base-spi:
+    description: SPI base of the MSI frame
+    $ref: /schemas/types.yaml#/definitions/uint32
+
+  al,msi-num-spis:
+    description: number of SPIs assigned to the MSI frame, relative to SPI0
+    $ref: /schemas/types.yaml#/definitions/uint32
+
+required:
+  - compatible
+  - reg
+  - msi-controller
+  - al,msi-base-spi
+  - al,msi-num-spis
+
+additionalProperties: false
+
+examples:
+  - |
+    msi-controller@fbe00000 {
+        compatible = "al,alpine-msix";
+        reg = <0xfbe00000 0x100000>;
+        interrupt-parent = <&gic>;
+        msi-controller;
+        al,msi-base-spi = <160>;
+        al,msi-num-spis = <160>;
+    };