net: smc911x: Add pkt_data_pull and pkt_data_push function

The RSK7203 board has the SMSC9118 wired up 'incorrectly'.
Byte-swapping is necessary, and so poor performance is inevitable.
This problem cannot evade by the swap function of CHIP, this can
evade by software Byte-swapping.
And this has problem by FIFO access only. pkt_data_pull/pkt_data_push
functions necessary to solve this problem.

Signed-off-by: Nobuhiro Iwamatsu <iwamatsu.nobuhiro@renesas.com>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>