dt-bindings: clean up rockchip grf binding document

Fixup some typos and inconsistencies in the grf binding.
Signed-off-by: Peter Geis <pgwipeout@gmail.com>
Link: https://lore.kernel.org/r/20191028182254.30739-3-pgwipeout@gmail.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

Documentation/devicetree/bindings/soc/rockchip/grf.txt

@@ -38,12 +38,12 @@ Required Properties:
    - "rockchip,px30-pmugrf", "syscon": for px30
    - "rockchip,rk3368-pmugrf", "syscon": for rk3368
    - "rockchip,rk3399-pmugrf", "syscon": for rk3399
-- compatible: SGRF should be one of the following
+- compatible: SGRF should be one of the following:
    - "rockchip,rk3288-sgrf", "syscon": for rk3288
-- compatible: USB2PHYGRF should be one of the followings
+- compatible: USB2PHYGRF should be one of the following:
    - "rockchip,px30-usb2phy-grf", "syscon": for px30
    - "rockchip,rk3328-usb2phy-grf", "syscon": for rk3328
-- compatible: USBGRF should be one of the following
+- compatible: USBGRF should be one of the following:
    - "rockchip,rv1108-usbgrf", "syscon": for rv1108
 - reg: physical base address of the controller and length of memory mapped
   region.