dt-bindings: More use 'enum' instead of 'oneOf' plus 'const' entries

'enum' is equivalent to 'oneOf' with a list of 'const' entries, but 'enum'
is more concise and yields better error messages.

Fix a couple more cases which have appeared.

Cc: Rob Clark <[e-mail]>
Cc: Sean Paul <[e-mail]>
Cc: Mark Brown <[e-mail]>
Cc: Wim Van Sebroeck <[e-mail]>
Cc: Guenter Roeck <[e-mail]>
Cc: Jonathan Marek <[e-mail]>
Cc: Aswath Govindraju <[e-mail]>
Cc: Marc Zyngier <[e-mail]>
Cc: Linus Walleij <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Signed-off-by: Rob Herring <[e-mail]>
Acked-by: Guenter Roeck <[e-mail]>
Acked-by: Mark Brown <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/devicetree/bindings/display/msm/dsi-phy-7nm.yaml

···
 
 properties:
   compatible:
-    oneOf:
-      - const: qcom,dsi-phy-7nm
-      - const: qcom,dsi-phy-7nm-8150
-      - const: qcom,sc7280-dsi-phy-7nm
+    enum:
+      - qcom,dsi-phy-7nm
+      - qcom,dsi-phy-7nm-8150
+      - qcom,sc7280-dsi-phy-7nm
 
   reg:
     items:

Documentation/devicetree/bindings/spi/omap-spi.yaml

···
 if:
   properties:
     compatible:
-      oneOf:
-        - const: ti,omap2-mcspi
-        - const: ti,omap4-mcspi
+      enum:
+        - ti,omap2-mcspi
+        - ti,omap4-mcspi
 
 then:
   properties:

Documentation/devicetree/bindings/watchdog/maxim,max63xx.yaml

···
 
 properties:
   compatible:
-    oneOf:
-      - const: maxim,max6369
-      - const: maxim,max6370
-      - const: maxim,max6371
-      - const: maxim,max6372
-      - const: maxim,max6373
-      - const: maxim,max6374
+    enum:
+      - maxim,max6369
+      - maxim,max6370
+      - maxim,max6371
+      - maxim,max6372
+      - maxim,max6373
+      - maxim,max6374
 
   reg:
     description: This is a 1-byte memory-mapped address