dt-bindings: cache: andestech,ax45mp-cache: Add DT binding documentation for L2 cache controller

Add DT binding documentation for L2 cache controller found on RZ/Five SoC.

The Renesas RZ/Five microprocessor includes a RISC-V CPU Core (AX45MP
Single) from Andes. The AX45MP core has an L2 cache controller, this patch
describes the L2 cache block.
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com> # tyre-kicking on a d1
Link: https://lore.kernel.org/r/20230818135723.80612-5-prabhakar.mahadev-lad.rj@bp.renesas.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Documentation/devicetree/bindings/cache/andestech,ax45mp-cache.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright (C) 2023 Renesas Electronics Corp.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/cache/andestech,ax45mp-cache.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Andestech AX45MP L2 Cache Controller
+
+maintainers:
+  - Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
+
+description:
+  A level-2 cache (L2C) is used to improve the system performance by providing
+  a large amount of cache line entries and reasonable access delays. The L2C
+  is shared between cores, and a non-inclusive non-exclusive policy is used.
+
+select:
+  properties:
+    compatible:
+      contains:
+        enum:
+          - andestech,ax45mp-cache
+
+  required:
+    - compatible
+
+properties:
+  compatible:
+    items:
+      - const: andestech,ax45mp-cache
+      - const: cache
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  cache-line-size:
+    const: 64
+
+  cache-level:
+    const: 2
+
+  cache-sets:
+    const: 1024
+
+  cache-size:
+    enum: [131072, 262144, 524288, 1048576, 2097152]
+
+  cache-unified: true
+
+  next-level-cache: true
+
+additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - cache-line-size
+  - cache-level
+  - cache-sets
+  - cache-size
+  - cache-unified
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    cache-controller@2010000 {
+        compatible = "andestech,ax45mp-cache", "cache";
+        reg = <0x13400000 0x100000>;
+        interrupts = <508 IRQ_TYPE_LEVEL_HIGH>;
+        cache-line-size = <64>;
+        cache-level = <2>;
+        cache-sets = <1024>;
+        cache-size = <262144>;
+        cache-unified;
+    };