aqc111: fix writing to the phy on BE

When writing to the phy on BE architectures an internal data structure
was directly given, leading to it being byte swapped in the wrong
way for the CPU in 50% of all cases. A temporary buffer must be used.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>