mlx4: use bitmap library

Replace loops calling set_bit() and clear_bit() with bitmap_set() and
bitmap_clear().

Unlike loops calling set_bit() and clear_bit(), bitmap_set() and
bitmap_clear() are not atomic. But this is ok.
Because the bitmap operations are protected by bitmap->lock
except for initialization of the bitmap in mlx4_bitmap_init().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Roland Dreier <rolandd@cisco.com>
Cc: netdev@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>