gianfar: use more portable i/o accessors

in/out_be32 accessors are Power arch centric whereas
ioread/writebe32 are available in other arches.  Also, unlike
in/out_be32, ioread/writebe32 expect non-volatile address arguments.

Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>