bnx2x: fix an error code in bnx2x_nic_load()

Set the error code if bnx2x_alloc_fw_stats_mem() fails.  The current
code returns success.

Fixes: ad5afc89 ("bnx2x: Separate VF and PF logic")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>