clk: Improve clock-indices binding documentation

Improve the wording for the clock-indices binding documentation.
Also replace "empty nodes" by "empty strings", as reported before by Sergei
Shtylyov.

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Acked-by: Laurent Pinchart <[e-mail]>
Acked-by: Simon Horman <[e-mail]>
Signed-off-by: Mike Turquette <[e-mail]>

Documentation/devicetree/bindings/clock/clock-bindings.txt

···
   clocks by index. The names should reflect the clock output signal
   names for the device.
 
-clock-indices:	   If the identifyng number for the clocks in the node
-		   is not linear from zero, then the this mapping allows
-		   the mapping of identifiers into the clock-output-names
-		   array.
+clock-indices:	   If the identifying number for the clocks in the node
+		   is not linear from zero, then this allows the mapping of
+		   identifiers into the clock-output-names array.
 
 For example, if we have two clocks <&oscillator 1> and <&oscillator 3>:
 
···
 		clock-output-names = "clka", "clkb";
 	}
 
-	This ensures we do not have any empty nodes in clock-output-names
+	This ensures we do not have any empty strings in clock-output-names
 
 
 ==Clock consumers==