net/mlx4_core: Fix VF overwrite of module param which disables DMFS on new probed PFs

In the VF driver, module parameter mlx4_log_num_mgm_entry_size was
mistakenly overwritten -- and in a manner which overrode the
device-managed flow steering option encoded in the parameter.

log_num_mgm_entry_size is a global module parameter which
affects all ConnectX-3 PFs installed on that host.
If a VF changes log_num_mgm_entry_size, this will affect all PFs
which are probed subsequent to the change (by disabling DMFS for
those PFs).

Fixes: 3c439b55

 ("mlx4_core: Allow choosing flow steering mode")
Signed-off-by: Majd Dibbiny <majd@mellanox.com>
Reviewed-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>