This adds the Intel e1000 driver from U-Boot. The driver looks in parts
quite similar to the kernel driver, I don't know whether one is derived
from the other or if they both just have the same origin.

Many coding style related issues are fixed, the code is simplified in
several places. All features of the original driver should still be there,
only fiber support is disabled since it's quite unlikely that this is
used in barebox.

The driver has been tested with the i.MX6 PCIe driver and a I210 e1000
device (0x8086:0x1533)

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>