cxgb4: fix set but unused variable when DCB is disabled

Remove the set but unused variable when DCB is disabled. Instead,
do the calculation directly inline.

Fixes following warning in make W=1:
cxgb4_main.c: In function 'cfg_queues':
cxgb4_main.c:5380:29: warning: variable 'n1g' set but not used
[-Wunused-but-set-variable]
  u32 i, n10g = 0, qidx = 0, n1g = 0;
                             ^

Fixes: 116ca924 ("cxgb4: fix checks for max queues to allocate")
Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>