mlxsw: Add return value check for mlxsw_sp_port_get_stats_raw()

mlxsw: Add return value check for mlxsw_sp_port_get_stats_raw()

Add a check for the return value of mlxsw_sp_port_get_stats_raw()
in __mlxsw_sp_port_get_stats(). If mlxsw_sp_port_get_stats_raw()
returns an error, exit the function to prevent further processing
with potentially invalid data.

Fixes: 614d509aa1e7 ("mlxsw: Move ethtool_ops to spectrum_ethtool.c")
Cc: stable@vger.kernel.org # 5.9+
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Link: https://patch.msgid.link/20250212152311.1332-1-vulab@iscas.ac.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>