mlxsw: spectrum: Avoid -Wformat-truncation warnings

mlxsw: spectrum: Avoid -Wformat-truncation warnings

Give precision identifiers to the two snprintf() formatting the priority
and TC strings to avoid producing these two warnings:

drivers/net/ethernet/mellanox/mlxsw/spectrum.c: In function
'mlxsw_sp_port_get_prio_strings':
drivers/net/ethernet/mellanox/mlxsw/spectrum.c:2132:37: warning: '%d'
directive output may be truncated writing between 1 and 3 bytes into a
region of size between 0 and 31 [-Wformat-truncation=]
   snprintf(*p, ETH_GSTRING_LEN, "%s_%d",
                                     ^~
drivers/net/ethernet/mellanox/mlxsw/spectrum.c:2132:3: note: 'snprintf'
output between 3 and 36 bytes into a destination of size 32
   snprintf(*p, ETH_GSTRING_LEN, "%s_%d",
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     mlxsw_sp_port_hw_prio_stats[i].str, prio);
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/mellanox/mlxsw/spectrum.c: In function
'mlxsw_sp_port_get_tc_strings':
drivers/net/ethernet/mellanox/mlxsw/spectrum.c:2143:37: warning: '%d'
directive output may be truncated writing between 1 and 11 bytes into a
region of size between 0 and 31 [-Wformat-truncation=]
   snprintf(*p, ETH_GSTRING_LEN, "%s_%d",
                                     ^~
drivers/net/ethernet/mellanox/mlxsw/spectrum.c:2143:3: note: 'snprintf'
output between 3 and 44 bytes into a destination of size 32
   snprintf(*p, ETH_GSTRING_LEN, "%s_%d",
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     mlxsw_sp_port_hw_tc_stats[i].str, tc);
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>