dt-bindings: bus: imx-weim: document optional burst clock mode

An optional devicetree property was added to the imx-weim driver,
which if present instructs it to operate in burst clock mode.
Update the dt-bindings to reflect this.

Signed-off-by: Sven Van Asbroeck <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

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

···
 			what bootloader sets up in IOMUXC_GPR1[11:0] will be
 			used.
 
+ - fsl,burst-clk-enable	For "fsl,imx50-weim" and "fsl,imx6q-weim" type of
+			devices, the presence of this property indicates that
+			the weim bus should operate in Burst Clock Mode.
+
 Timing property for child nodes. It is mandatory, not optional.
 
  - fsl,weim-cs-timing:	The timing array, contains timing values for the