qlcnic: dcb: a couple off by one bugs

The ->tc_cfg[] array has QLC_DCB_MAX_TC (8) elements so the check is
off by one.  These functions are always called with valid values though
so it doesn't affect how the code works.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Sucheta Chakraborty <sucheta.chakraborty@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>