net/mlx5: Reduce flow counters bulk query buffer size for SFs

Currently, the flow counters bulk query buffer takes a little more than
512KB of memory, which is aligned to the next power of 2, to 1MB.

The buffer size determines the maximum number of flow counters that can
be queried at a time. Thus, having a bigger buffer can improve
performance for users that need to query many flow counters.

SFs don't use many flow counters and don't need a big buffer. Since this
size is critical with large scale, reduce the size of the bulk query
buffer for SFs.

Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>