mlxsw: spectrum_kvdl: Make some functions static

Fixes the following sparse warnings:

drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c:371:5: warning:
 symbol 'mlxsw_sp_kvdl_single_occ_get' was not declared. Should it be static?
drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c:384:5: warning:
 symbol 'mlxsw_sp_kvdl_chunks_occ_get' was not declared. Should it be static?
drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c:397:5: warning:
 symbol 'mlxsw_sp_kvdl_large_chunks_occ_get' was not declared. Should it be static?

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>