dts: bindings: trivial clock bindings doc fixes

fix a typo in the "clock specifiers" discussion,
clarify that clock specifiers (the integer cells
part that goes with the phandle) may be empty

Cc: Rob Herring <[e-mail]>
Cc: Pawel Moll <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Stephen Warren <[e-mail]>
Cc: Ian Campbell <[e-mail]>
Cc: [e-mail]
Acked-by: Mark Rutland <[e-mail]>
Signed-off-by: Gerhard Sittig <[e-mail]>
Signed-off-by: Rob Herring <[e-mail]>

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

···
 tree.  Those nodes are designated as clock providers.  Clock consumer
 nodes use a phandle and clock specifier pair to connect clock provider
 outputs to clock inputs.  Similar to the gpio specifiers, a clock
-specifier is an array of one more more cells identifying the clock
+specifier is an array of zero, one or more cells identifying the clock
 output on a device.  The length of a clock specifier is defined by the
 value of a #clock-cells property in the clock provider node.