dt-bindings: rtc: Fix Xicor X1205 vendor prefix

The vendor for the Xircom X1205 RTC is not Xircom, but Xicor which was
acquired by Intersil.

Signed-off-by: Rob Herring (Arm) <[e-mail]>
Reviewed-by: Linus Walleij <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexandre Belloni <[e-mail]>

Documentation/devicetree/bindings/rtc/trivial-rtc.yaml

···
       - via,vt8500-rtc
       # I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
       - whwave,sd3078
-      # Xircom X1205 I2C RTC
-      - xircom,x1205
+      # Xicor/Intersil X1205 I2C RTC
+      - xicor,x1205
 
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