mlxsw: spectrum: Fix memory leak in mlxsw_sp_flower_stats()

mlxsw: spectrum: Fix memory leak in mlxsw_sp_flower_stats()

The function mlxsw_sp_flower_stats() calls mlxsw_sp_acl_ruleset_get() to
obtain a ruleset reference. If the subsequent call to
mlxsw_sp_acl_rule_lookup() fails to find a rule, the function returns
an error without releasing the ruleset reference, causing a memory leak.

Fix this by using a goto to the existing error handling label, which
calls mlxsw_sp_acl_ruleset_put() to properly release the reference.

Fixes: 7c1b8eb175b69 ("mlxsw: spectrum: Add support for TC flower offload statistics")
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20251112052114.1591695-1-zilin@seu.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>