net/mlx5: Fix return value when searching for existing flow group

When attempting to add a rule to an existing flow group, if a matching
flow group exists but is not active, the error code returned should be
EAGAIN, so that the rule can be added to the matching flow group once
it is active, rather than ENOENT, which indicates that no matching
flow group was found.

Fixes: bd71b08e ("net/mlx5: Support multiple updates of steering rules in parallel")
Signed-off-by: Gavi Teitz <gavi@nvidia.com>
Signed-off-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Patrisious Haddad <phaddad@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Mark Bloch <mbloch@nvidia.com>
Link: https://patch.msgid.link/20250610151514.1094735-4-mbloch@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>