uboot-imx

net: Add ethernet FCS length macro in net.h

Some ethernet drivers use their own version of ethernet FCS length
macro which is really common. We define ETH_FCS_LEN in net.h and
replace those custom versions in various places.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>