cxgb4: add cxgb4_fcoe.h and macro definitions for FCoE

This patch adds new header file cxgb4_fcoe.h and defines new
macros for FCoE support in cxgb4 driver.

Signed-off-by: Varun Prakash <varun@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>