amd-xgbe: Remove use of comm_owned field

The comm_owned field can hide logic where double locking is attempted
and prevent multiple threads for the same device from accessing the
mutex properly.  Remove the comm_owned field and use the mutex API
exclusively for gaining ownership.  The current driver has been audited
and is obtaining communications ownership properly.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>