IB/mlx5: Fix the size parameter to find_first_bit

IB/mlx5: Fix the size parameter to find_first_bit

The 2nd parameter of 'find_first_bit' is the number of bits to search.
In this case, we are passing 'sizeof(tmp)' which is likely to be 4 or 8
because 'tmp' is an 'unsigned long'.

It is likely that the number of bits of 'tmp' was expected here. So use
BITS_PER_LONG instead.

It has been spotted by the following coccinelle script:
@@
expression ret, x;

@@
*  ret = \(find_first_bit \| find_first_zero_bit\) (x, sizeof(...));

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Majd Dibbiny <majd@mellanox.com>
Acked-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>