net/mlx4: fix sparse warnings on TX blue flame buffer

The blue flame buffer is defined to be of type void __iomem *
but was passed to mlx4_bf_copy which gets unsigned long * .
This triggered sparse warning on different address spaces,
fix that by changing mlx4_bf_copy first param to be of type void __iomem * .

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>