qlcnic: silence false positive overflow warning

We actually store the MAC address as well as the board_name here.  The
longest board_name is 75 characters so there is more than enough room
to hold the 17 character MAC and the ": " divider.  But making this
buffer larger silences a static checker warning.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-By: Jitendra Kalsaria <jitendra.kalsaria@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>