qed: Fix possible memory leak in Rx error path handling.

Memory for packet buffers need to be freed in the error paths as there is
no consumer (e.g., upper layer) for such packets and that memory will never
get freed.
The issue was uncovered when port was attacked with flood of isatap
packets, these are multicast packets hence were directed at all the PFs.
For foce PF, this meant they were routed to the ll2 module which in turn
drops such packets.

Fixes: 0a7fb11c ("qed: Add Light L2 support")
Signed-off-by: Sudarsana Reddy Kalluru <Sudarsana.Kalluru@cavium.com>
Signed-off-by: Ariel Elior <ariel.elior@cavium.com>
Signed-off-by: Michal Kalderon <Michal.Kalderon@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>