devicetree: bindings: ARM: Use "uV" for micro-volt

The binding documentation uses both "uVolt" and "uV" for micro-volt.
Improve consistency by settling on "uV".
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NRob Herring <robh@kernel.org>

Documentation/devicetree/bindings/arm/cpus.txt

@@ -250,7 +250,7 @@ nodes to be present and contain the properties described below.
 		Usage: optional
 		Value type: <prop-encoded-array>
 		Definition: A u32 value that represents the running time dynamic
-			    power coefficient in units of mW/MHz/uVolt^2. The
+			    power coefficient in units of mW/MHz/uV^2. The
 			    coefficient can either be calculated from power
 			    measurements or derived by analysis.