MFC r327254, r327904, and r328994.

r327254:
cxgbe/iw_cxgbe: Fix iWARP over VLANs (catch up with r326169).

r327904:
cxgbe/iw_cxgbe: Remove duplicates to fix compilation with recent gcc.

r328994:
iw_cxgbe: Remove declaration of a function that no longer exists.

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