dt-bindings: fec: update the gpr property

- rename the 'gpr' property string to 'fsl,stop-mode'.
- Update the property to define gpr register offset and
bit in DT, since different instance have different gpr bit.

v2:
 * rename 'gpr' property string to 'fsl,stop-mode'.
Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/fsl-fec.txt

@@ -22,8 +22,11 @@ Optional properties:
 - fsl,err006687-workaround-present: If present indicates that the system has
   the hardware workaround for ERR006687 applied and does not need a software
   workaround.
-- gpr: phandle of SoC general purpose register mode. Required for wake on LAN
-  on some SoCs
+- fsl,stop-mode: register bits of stop mode control, the format is
+		 <&gpr req_gpr req_bit>.
+		 gpr is the phandle to general purpose register node.
+		 req_gpr is the gpr register offset for ENET stop request.
+		 req_bit is the gpr bit offset for ENET stop request.
  -interrupt-names:  names of the interrupts listed in interrupts property in
   the same order. The defaults if not specified are
   __Number of interrupts__   __Default__