qlcnic: dcb code cleanup and refactoring.

o Move dcb specific function definitions to dcb files.
o Move dcb specific variables to qlcnic_dcb structure.

Signed-off-by: Sucheta Chakraborty <sucheta.chakraborty@qlogic.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>