cxgb3: Removing unused return variable

Currently the ret variable is not used for anything other than
receive the value of the t3_adapter_error(), which will always be 0,
because the reset parameter is 0.

Signed-off-by: Breno Leitao <leitao@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>