cxgb4: fix MPS index overwrite when setting MAC address

cxgb4_update_mac_filt() earlier requests firmware to add a new MAC
address into MPS TCAM. The MPS TCAM index returned by firmware is
stored in pi->xact_addr_filt. However, the saved MPS TCAM index gets
overwritten again with the return value of cxgb4_update_mac_filt(),
which is wrong.

When trying to update to another MAC address later, the wrong MPS TCAM
index is sent to firmware, which causes firmware to return error,
because it's not the same MPS TCAM index that firmware had sent
earlier to driver.

So, fix by removing the wrong overwrite being done after call to
cxgb4_update_mac_filt().

Fixes: 3f8cfd0d95e6 ("cxgb4/cxgb4vf: Program hash region for {t4/t4vf}_change_mac()")
Signed-off-by: Herat Ramani <herat@chelsio.com>
Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>