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/mpc832x_mds.dts

@@ -356,13 +356,11 @@
 				interrupt-parent = <&ipic>;
 				interrupts = <17 0x8>;
 				reg = <0x3>;
-				device_type = "ethernet-phy";
 			};
 			phy4: ethernet-phy@04 {
 				interrupt-parent = <&ipic>;
 				interrupts = <18 0x8>;
 				reg = <0x4>;
-				device_type = "ethernet-phy";
 			};
 		};