enic: add Cisco 10G Ethernet NIC driver

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drivers/net/Kconfig

drivers/net/Makefile

drivers/net/enic/Makefile

drivers/net/enic/cq_desc.h

drivers/net/enic/cq_enet_desc.h

drivers/net/enic/enic.h

drivers/net/enic/enic_main.c

drivers/net/enic/enic_res.c

drivers/net/enic/enic_res.h

drivers/net/enic/rq_enet_desc.h

drivers/net/enic/vnic_cq.c

drivers/net/enic/vnic_cq.h

drivers/net/enic/vnic_dev.c

drivers/net/enic/vnic_dev.h

drivers/net/enic/vnic_devcmd.h

drivers/net/enic/vnic_enet.h

drivers/net/enic/vnic_intr.c

drivers/net/enic/vnic_intr.h

drivers/net/enic/vnic_nic.h