dt-bindings: net: qcom,ipa: do not override firmware-name $ref

dtschema package defines firmware-name as string-array, so individual
bindings should not make it a string but instead just narrow the number
of expected firmware file names.

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Acked-by: Conor Dooley <[e-mail]>
Acked-by: Alex Elder <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

Documentation/devicetree/bindings/net/qcom,ipa.yaml

···
       when the AP (not the modem) performs early initialization.
 
   firmware-name:
-    $ref: /schemas/types.yaml#/definitions/string
+    maxItems: 1
     description:
       If present, name (or relative path) of the file within the
       firmware search path containing the firmware image used when