libethdrivers: Update license headers

These license headers were copied from other sources prior to them being updated.
This commit is simply applying the same updates to these copies

Grabbed common files from Data61's i.MX6 driver.

Since the driver structure between the i.MX6 and the Zynq7000
is very similar, it would be nice to have a new directory for
source files that is arch/arm. However, all the files in the
u-boot directory reference headers locally, and including these
files in the plat_include or arch_include directory makes it
nearly impossible to reference local files. This is something
to do at a later time.

Change-Id: Ic37753496680a6975f2ea6f25bb5049459b14183