dt-bindings: clk: oxnas: remove obsolete bindings

Due to lack of maintenance and stall of development for a few years now,
and since no new features will ever be added upstream, remove the
OX810 and OX820 clock bindings.
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20230630-topic-oxnas-upstream-remove-v2-2-fb6ab3dea87c@linaro.orgSigned-off-by: Stephen Boyd <sboyd@kernel.org>

Documentation/devicetree/bindings/clock/oxnas,stdclk.txt

-Oxford Semiconductor OXNAS SoC Family Standard Clocks
-================================================
-
-Please also refer to clock-bindings.txt in this directory for common clock
-bindings usage.
-
-Required properties:
-- compatible: For OX810SE, should be "oxsemi,ox810se-stdclk"
-	      For OX820, should be "oxsemi,ox820-stdclk"
-- #clock-cells: 1, see below
-
-Parent node should have the following properties :
-- compatible: For OX810SE, should be
-		"oxsemi,ox810se-sys-ctrl", "syscon", "simple-mfd"
-	      For OX820, should be
-		"oxsemi,ox820-sys-ctrl", "syscon", "simple-mfd"
-
-example:
-
-sys: sys-ctrl@000000 {
-	compatible = "oxsemi,ox810se-sys-ctrl", "syscon", "simple-mfd";
-	reg = <0x000000 0x100000>;
-
-	stdclk: stdclk {
-		compatible = "oxsemi,ox810se-stdclk";
-		#clock-cells = <1>;
-	};
-};