mlxsw: spectrum: Make function mlxsw_sp_kvdl_part_occ() static

Fixes the following sparse warning:

drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c:289:5: warning:
 symbol 'mlxsw_sp_kvdl_part_occ' was not declared. Should it be static?

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Arkadi Sharshevsky <arkadis@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>