spi: dt-bindings: brcm,bcm2835-spi: convert to dtschema

Convert the Broadcom BCM2835 SPI0 controller to newer DT
schema. Created DT schema based on the .txt file which had
`comaptible`, `reg`, `interrupts`, `clocks` as required
properties.
Added GPL-2.0 OR BSD-2-Clause License

Signed-off-by: Kanak Shilledar <[e-mail]>
Reviewed-by: Conor Dooley <[e-mail]>
Link: https://msgid.link/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

Documentation/devicetree/bindings/spi/brcm,bcm2835-spi.txt

···
-Broadcom BCM2835 SPI0 controller
-
-The BCM2835 contains two forms of SPI master controller, one known simply as
-SPI0, and the other known as the "Universal SPI Master"; part of the
-auxiliary block. This binding applies to the SPI0 controller.
-
-Required properties:
-- compatible: Should be one of "brcm,bcm2835-spi" for BCM2835/2836/2837 or
-  "brcm,bcm2711-spi" for BCM2711 or "brcm,bcm7211-spi" for BCM7211.
-- reg: Should contain register location and length.
-- interrupts: Should contain interrupt.
-- clocks: The clock feeding the SPI controller.
-
-Example:
-
-spi@20204000 {
-	compatible = "brcm,bcm2835-spi";
-	reg = <0x7e204000 0x1000>;
-	interrupts = <2 22>;
-	clocks = <&clk_spi>;
-	#address-cells = <1>;
-	#size-cells = <0>;
-};

Documentation/devicetree/bindings/spi/brcm,bcm2835-spi.yaml

···
+# SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/spi/brcm,bcm2835-spi.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Broadcom BCM2835 SPI0 controller
+
+maintainers:
+  - Florian Fainelli <[e-mail]>
+  - Kanak Shilledar <[e-mail]>
+  - Stefan Wahren <[e-mail]>
+
+allOf:
+  - $ref: spi-controller.yaml#
+
+properties:
+  compatible:
+    enum:
+      - brcm,bcm2835-spi
+      - brcm,bcm2711-spi
+      - brcm,bcm7211-spi
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    spi@20204000 {
+        compatible = "brcm,bcm2835-spi";
+        reg = <0x7e204000 0x1000>;
+        interrupts = <2 22>;
+        clocks = <&clk_spi>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+    };