this patch fixes following sparse warning:

cxgb4_dcb.c:25:6: warning: symbol 'dcb_ver_array' was not declared. Should it be static?

Alongside making it const.
Signed-off-by: NLad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>