dt-bindings: bus: imx-weim: add words about continuous bclk

Document continuous Burst Clock option. With this option Burst Clock, if
enabled, will output continuous clock, otherwise Burst Clock will output
clock only when necessary.

Signed-off-by: Ivan Bornyakov <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

Documentation/devicetree/bindings/bus/imx-weim.txt

···
 			devices, the presence of this property indicates that
 			the weim bus should operate in Burst Clock Mode.
 
+ - fsl,continuous-burst-clk	Make Burst Clock to output continuous clock.
+			Without this option Burst Clock will output clock
+			only when necessary. This takes effect only if
+			"fsl,burst-clk-enable" is set.
+
 Timing property for child nodes. It is mandatory, not optional.
 
  - fsl,weim-cs-timing:	The timing array, contains timing values for the