bnxt_en: fix memory leaks in bnxt_dcbnl_ieee_getets()

The allocated ieee_ets structure goes out of scope without being freed,
leaking memory. Appropriate result codes should be returned so that
callers do not rely on invalid data passed by reference.

Also cache the ETS config retrieved from the device so that it doesn't
need to be freed. The balance of the code was clearly written with the
intent of having the results of querying the hardware cached in the
device structure. The commensurate store was evidently missed though.

Fixes: 7df4ae9f ("bnxt_en: Implement DCBNL to support host-based DCBX.")
Signed-off-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>