The 'phy' reset of gmac device in kernel device tree is not generic
enough for u-boot to use, so we need to overwrite the 'resets' property
as needed.  With this device tree fixup and poplar_defconfig changes,
Ethernet starts working on Poplar board.
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>
Acked-by: NJoe Hershberger <joe.hershberger@ni.com>