net/mlx5: DR, Fix uninitialized var warning

stable inclusion
from stable-v5.10.158
commit 2b1d8f27e2051d9d35043edbf2e3f4e1354edf59
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7NTXH

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2b1d8f27e2051d9d35043edbf2e3f4e1354edf59



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[ Upstream commit 52f7cf70 ]

Smatch warns this:

drivers/net/ethernet/mellanox/mlx5/core/steering/dr_table.c:81
 mlx5dr_table_set_miss_action() error: uninitialized symbol 'ret'.

Initializing ret with -EOPNOTSUPP and fix missing action case.

Fixes: 7838e172 ("net/mlx5: DR, Expose steering table functionality")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>