dt-bindings: qcom,pdc: Add compatible for SM8250

Add the compatible string for SM8250 SoC from Qualcomm. This compatible
is used already in DTS files but not documented yet
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210115090941.2289416-1-vkoul@kernel.org

Documentation/devicetree/bindings/interrupt-controller/qcom,pdc.txt

@@ -20,6 +20,7 @@ Properties:
 	Definition: Should contain "qcom,<soc>-pdc" and "qcom,pdc"
 		    - "qcom,sc7180-pdc": For SC7180
 		    - "qcom,sdm845-pdc": For SDM845
+		    - "qcom,sdm8250-pdc": For SM8250
 
 - reg:
 	Usage: required