dt-bindings: iio: dac: fix ad3552r gain parameter names

The adi,gain-scaling-p/n values are an inverted log2,
so initial naming was set correctly, but the driver uses just
adi,gain-scaling-p/n, and if fdt is created accordingly with
the fdt bindings documentation, driver fails the probe.

Observing that:
- the Linux driver is the only consumer,
- there are no upstreamed dts nodes related to ad3552r,

the fix to the documentation side is preferred and less-risk.

Fixes: b0a96c5f ("dt-bindings: iio: dac: Add adi,ad3552r.yaml")
Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240522150141.1776196-2-adureghello@baylibre.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml

@@ -92,13 +92,13 @@ patternProperties:
             maximum: 511
             minimum: -511
 
-          adi,gain-scaling-p-inv-log2:
-            description: GainP = 1 / ( 2 ^ adi,gain-scaling-p-inv-log2)
+          adi,gain-scaling-p:
+            description: GainP = 1 / ( 2 ^ adi,gain-scaling-p)
             $ref: /schemas/types.yaml#/definitions/uint32
             enum: [0, 1, 2, 3]
 
-          adi,gain-scaling-n-inv-log2:
-            description: GainN = 1 / ( 2 ^ adi,gain-scaling-n-inv-log2)
+          adi,gain-scaling-n:
+            description: GainN = 1 / ( 2 ^ adi,gain-scaling-n)
             $ref: /schemas/types.yaml#/definitions/uint32
             enum: [0, 1, 2, 3]
 
@@ -107,8 +107,8 @@ patternProperties:
 
         required:
           - adi,gain-offset
-          - adi,gain-scaling-p-inv-log2
-          - adi,gain-scaling-n-inv-log2
+          - adi,gain-scaling-p
+          - adi,gain-scaling-n
           - adi,rfb-ohms
 
     required:
@@ -208,8 +208,8 @@ examples:
                 reg = <1>;
                 custom-output-range-config {
                     adi,gain-offset = <5>;
-                    adi,gain-scaling-p-inv-log2 = <1>;
-                    adi,gain-scaling-n-inv-log2 = <2>;
+                    adi,gain-scaling-p = <1>;
+                    adi,gain-scaling-n = <2>;
                     adi,rfb-ohms = <1>;
                 };
             };