octeontx2-af: Copy the right amount of memory

This is a copy and paste bug where we copied the sizeof() from the chunk
before.  We're copying more data than intended but the destination is a
union so it doesn't cause memory corruption.

Fixes: ffb0abd7

 ("octeontx2-af: NIX AQ instruction enqueue support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>