mlxsw: spectrum: Don't emit errors when PFC is disabled

We can't have PAUSE frames and PFC both enabled on the same port, but
the fact that ieee_setpfc() was called doesn't necessarily mean PFC is
enabled.

Only emit errors when PAUSE frames and PFC are enabled simultaneously.

Fixes: d81a6bdb

 ("mlxsw: spectrum: Add IEEE 802.1Qbb PFC support")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>