net/mlx5: DR, Fix potential race in dr_rule_create_rule_nic

Selecting builder should be protected by the lock to prevent the case
where a new rule sets a builder in the nic_matcher while the previous
rule is still using the nic_matcher.

Fixing this issue and cleaning the error flow.

Fixes: b9b81e1e

 ("net/mlx5: DR, For short chains of STEs, avoid allocating ste_arr dynamically")
Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Reviewed-by: Alex Vesker <valex@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>