dt/bindings: Remove all references to device_type "ethernet-phy"

The device_type property is deprecated for the flattened device tree and
the value "ethernet-phy" has never been defined as having a useful
meaning. Neither the kernel nor u-boot depend on it. It should never
have appeared in PHY bindings. This patch removes all references to
"ethernet-phy" as a device_type value from the documentation and the
.dts files.

This patch was generated mechanically with the following command and
then verified by looking at the diff.

sed -i '/"ethernet-phy"/d' `git grep -l '"ethernet-phy"'`

Signed-off-by: Grant Likely <grant.likely@linaro.org>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Kumar Gala <galak@codeaurora.org>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/boot/dts/mpc8540ads.dts

@@ -165,19 +165,16 @@
 					interrupt-parent = <&mpic>;
 					interrupts = <5 1>;
 					reg = <0x0>;
-					device_type = "ethernet-phy";
 				};
 				phy1: ethernet-phy@1 {
 					interrupt-parent = <&mpic>;
 					interrupts = <5 1>;
 					reg = <0x1>;
-					device_type = "ethernet-phy";
 				};
 				phy3: ethernet-phy@3 {
 					interrupt-parent = <&mpic>;
 					interrupts = <7 1>;
 					reg = <0x3>;
-					device_type = "ethernet-phy";
 				};
 				tbi0: tbi-phy@11 {
 					reg = <0x11>;