When using ethernet DM driver, the recv interface has a change with non-DM
interface, that driver needs to set the packet pointer and provide it to upper
layer to process.
In fec driver, the fecmxc_recv functions does not handle the packet pointer parameter.
This may cause crash in upper layer processing because the packet pointer is not set.

This patch allocates a buffer for the packet pointer and free it through free_pkt interface.

Signed-off-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>