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 <[e-mail]>
Reviewed-by: Bjorn Andersson <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

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

···
 	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