dt/bindings: remove device_type "network" references

device_type is deprecated and the kernel doesn't require it in most
cases. The only exceptions for flat tree users are the "gianfar",
"ucc_geth" and "ibm,emac" bindings, and arguably that requirement could
be relaxed for ucc_geth and ibm,emac (that is a task for separate
patches though).

This patch removes references to device_type="network" from the binding
documentation where possible and removes the properties from ARM and
microblaze dts files. This patch does not modify the powerpc .dts files
since there are a much larger number of them affected and I think the
ucc_geth, ibm,emac and gianfar users should be addressed before clearing
out the references to reduce the chance of breakage.

Signed-off-by: Grant Likely <grant.likely@linaro.org>
Acked-by: Michal Simek <monstr@monstr.eu>
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>