Fixed speed mode is not supported currently, this patch
removes configurations for this mode and adds fault handling
for ETH_LINK_SPEED_FIXED.
Fixes: 4f09bc55ac3d ("net/igc: implement device base operations")
Cc: stable@dpdk.org
Signed-off-by: Alvin Zhang <alvinx.zhang@intel.com>
Acked-by: Junfeng Guo <junfeng.guo@intel.com>