dt-bindings: clock: fsl-sai: Document clock-cells = <1> support

The driver now supports generation of both BCLK and MCLK, document
support for #clock-cells = <0> for legacy case and #clock-cells = <1>
for the new case which can differentiate between BCLK and MCLK.

Acked-by: Conor Dooley <[email protected]>
Signed-off-by: Marek Vasut <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>

Author: Marek Vasut

Documentation/devicetree/bindings/clock/fsl,sai-clock.yaml

@@ -10,7 +10,7 @@ maintainers:
   - Michael Walle <[email protected]>
 
 description: |
-  It is possible to use the BCLK pin of a SAI module as a generic
+  It is possible to use the BCLK or MCLK pin of a SAI module as a generic
   clock output. Some SoC are very constrained in their pin multiplexer
   configuration. E.g. pins can only be changed in groups. For example, on
   the LS1028A SoC you can only enable SAIs in pairs. If you use only one SAI,
@@ -47,7 +47,7 @@ properties:
       - const: mclk1
 
   '#clock-cells':
-    const: 0
+    maximum: 1
 
 allOf:
   - if: