dt-bindings: dsp: mediatek: Use meaningful names for mbox

Rename mbox according to actions instead of 'mbox0' and 'mbox1'.
The 8195 dsp node, which uses this binding, has not yet been added to
the 8195 devicetree.

Signed-off-by: Tinghan Shen <tinghan.shen@mediatek.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220622062245.21021-2-tinghan.shen@mediatek.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/dsp/mediatek,mt8195-dsp.yaml

@@ -50,13 +50,13 @@ properties:
 
   mboxes:
     items:
-      - description: ipc reply between host and audio DSP.
-      - description: ipc request between host and audio DSP.
+      - description: mailbox for receiving audio DSP requests.
+      - description: mailbox for transmitting requests to audio DSP.
 
   mbox-names:
     items:
-      - const: mbox0
-      - const: mbox1
+      - const: rx
+      - const: tx
 
   memory-region:
     items:
@@ -100,6 +100,6 @@ examples:
        memory-region = <&adsp_dma_mem_reserved>,
                        <&adsp_mem_reserved>;
        power-domains = <&spm 6>; //MT8195_POWER_DOMAIN_ADSP
-       mbox-names = "mbox0", "mbox1";
+       mbox-names = "rx", "tx";
        mboxes = <&adsp_mailbox0>, <&adsp_mailbox1>;
     };