mtd: gpmi: Remove "We support only one NAND chip" from bindings doc

This sentence "We support only one NAND chip now" is not true any more.
Multiple chips are supported. So lets remove this sentence to not
confuse anyone.
Signed-off-by: NStefan Roese <sr@denx.de>
Cc: Huang Shijie <b32955@freescale.com>
Cc: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: NBrian Norris <computersforpeace@gmail.com>

Documentation/devicetree/bindings/mtd/gpmi-nand.txt

 * Freescale General-Purpose Media Interface (GPMI)
 
 The GPMI nand controller provides an interface to control the
-NAND flash chips. We support only one NAND chip now.
+NAND flash chips.
 
 Required properties:
   - compatible : should be "fsl,<chip>-gpmi-nand"