dt-bindings: fsi-master-gpio: Document "no-gpio-delays" property

Support for this is being added to the driver but the original
patch forgot to add this documentation.

Signed-off-by: Benjamin Herrenschmidt <[e-mail]>
Signed-off-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/fsi/fsi-master-gpio.txt

···
  - trans-gpios = <gpio-descriptor>;	: GPIO for voltage translator enable
  - mux-gpios = <gpio-descriptor>;	: GPIO for pin multiplexing with other
                                           functions (eg, external FSI masters)
+ - no-gpio-delays;			: Don't add extra delays between GPIO
+                                          accesses. This is useful when the HW
+					  GPIO block is running at a low enough
+					  frequency.
 
 Examples: