mlx4: sizeof style usage

The kernel coding style is to treat sizeof as a function
(ie. with parenthesis) not as an operator.

Also use kcalloc and kmalloc_array

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>