usbnet: smsc95xx: fix memcpy for accessing rx-data

Change the RX code to use get_unaligned_le32() instead of the combo
of memcpy and cpu_to_le32s(&var).

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>