cxgb4: remove set but not used variables 'multitrc, speed'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/ethernet/chelsio/cxgb4/t4_hw.c:5883:6:
 warning: variable 'multitrc' set but not used [-Wunused-but-set-variable]

drivers/net/ethernet/chelsio/cxgb4/t4_hw.c:8585:32:
 warning: variable 'speed' set but not used [-Wunused-but-set-variable]

'multitrc' never used since introduction in
commit 8e3d04fd ("cxgb4: Add MPS tracing support")

'speed' never used since introduction in
commit c3168cab

 ("cxgb4/cxgbvf: Handle 32-bit fw port capabilities")

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>