dt-bindings: arm: mstar: remove the binding description for mstar,pmsleep

Remove the unneeded binding description.
Compatible string is in mfd/syscon.yaml now.

Link: https://lore.kernel.org/r/20200729150748.1945589-3-daniel@0x0f.comSigned-off-by: Daniel Palmer <daniel@0x0f.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Documentation/devicetree/bindings/arm/mstar/mstar,pmsleep.yaml

-# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
-# Copyright 2020 thingy.jp.
-%YAML 1.2
----
-$id: "http://devicetree.org/schemas/arm/mstar/mstar,pmsleep.yaml#"
-$schema: "http://devicetree.org/meta-schemas/core.yaml#"
-
-title: MStar/SigmaStar Armv7 SoC pmsleep register region
-
-maintainers:
-  - Daniel Palmer <daniel@thingy.jp>
-
-description: |
-  MStar/Sigmastar's Armv7 SoCs contain a region of registers that are
-  in the always on domain that the vendor code calls the "pmsleep" area.
-
-  This area contains registers and bits for a broad range of functionality
-  ranging from registers that control going into deep sleep to bits that
-  turn things like the internal temperature sensor on and off.
-
-properties:
-  compatible:
-    oneOf:
-      - items:
-         - enum:
-             - mstar,pmsleep
-         - const: syscon
-
-  reg:
-    maxItems: 1
-
-required:
-  - compatible
-  - reg
-
-additionalProperties: false
-
-examples:
-  - |
-    pmsleep: pmsleep@1c00 {
-        compatible = "mstar,pmsleep", "syscon";
-        reg = <0x0x1c00 0x100>;
-    };