aqc111: fix endianness issue in aqc111_change_mtu

If the MTU is large enough, the first write to the device
is just repeated. On BE architectures, however, the first
word of the command will be swapped a second time and garbage
will be written. Avoid that.

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