dt-bindings: phy: add binding for Allwinner H6 USB2 PHY

The USB2.0 PHY on Allwinner H6 is similar to the ones on the ones on
older SoCs, but with holes in PHY number (USB1 and USB2 are missing, in
which USB1 is a USB3 PHY).

Add binding for the PHY.

Signed-off-by: Icenowy Zheng <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Kishon Vijay Abraham I <[e-mail]>

Documentation/devicetree/bindings/phy/sun4i-usb-phy.txt

···
   * allwinner,sun8i-r40-usb-phy
   * allwinner,sun8i-v3s-usb-phy
   * allwinner,sun50i-a64-usb-phy
+  * allwinner,sun50i-h6-usb-phy
 - reg : a list of offset + length pairs
 - reg-names :
   * "phy_ctrl"
-  * "pmu0" for H3, V3s and A64
+  * "pmu0" for H3, V3s, A64 or H6
   * "pmu1"
   * "pmu2" for sun4i, sun6i, sun7i, sun8i-a83t or sun8i-h3
-  * "pmu3" for sun8i-h3
+  * "pmu3" for sun8i-h3 or sun50i-h6
 - #phy-cells : from the generic phy bindings, must be 1
 - clocks : phandle + clock specifier for the phy clocks
 - clock-names :
···
   * "usb0_phy", "usb1_phy" for sun8i
   * "usb0_phy", "usb1_phy", "usb2_phy" and "usb2_hsic_12M" for sun8i-a83t
   * "usb0_phy", "usb1_phy", "usb2_phy" and "usb3_phy" for sun8i-h3
+  * "usb0_phy" and "usb3_phy" for sun50i-h6
 - resets : a list of phandle + reset specifier pairs
 - reset-names :
   * "usb0_reset"
   * "usb1_reset"
   * "usb2_reset" for sun4i, sun6i, sun7i, sun8i-a83t or sun8i-h3
-  * "usb3_reset" for sun8i-h3
+  * "usb3_reset" for sun8i-h3 and sun50i-h6
 
 Optional properties:
 - usb0_id_det-gpios : gpio phandle for reading the otg id pin value