octeontx2-pf: unlock on error path in otx2_config_pause_frm()

We need to unlock before returning if this allocation fails.

Fixes: 75f36270 ("octeontx2-pf: Support to enable/disable pause frames via ethtool")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>