net/mlx5: Fix flow counters SF bulk query len

When doing a flow counters bulk query, the number of counters to query
must be aligned to 4. Current SF bulk query len is not aligned to 4,
which leads to an error when trying to query more than 4 counters.

Fix it by aligning SF bulk query len to 4.

Fixes: 2fdeb4f4

 ("net/mlx5: Reduce flow counters bulk query buffer size for SFs")
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>