arm: kirkwood: See to it that sent data is 8-byte aligned

U-boot might use non-8-byte-aligned addresses for sending data, which
the kwgbe_send doesn't accept (bootp does this for me). This patch
copies the data to be sent to a malloced temporary buffer if it is
non-aligned.

Signed-off-by: Simon Kagstrom <simon.kagstrom@netinsight.net>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>