net/mlx5e: Enable adding peer miss rules only if merged eswitch is supported

The cited commit creates peer miss group during switchdev mode
initialization in order to handle miss packets correctly while in VF
LAG mode. This is done regardless of FW support of such groups which
could cause rules setups failure later on.

Fix by adding FW capability check before creating peer groups/rule.

Fixes: ac004b83 ("net/mlx5e: E-Switch, Add peer miss rules")
Signed-off-by: Maor Dickman <maord@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Raed Salem <raeds@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>