dpaa2-switch: validate num_ifs to prevent out-of-bounds write

dpaa2-switch: validate num_ifs to prevent out-of-bounds write

The driver obtains sw_attr.num_ifs from firmware via dpsw_get_attributes()
but never validates it against DPSW_MAX_IF (64). This value controls
iteration in dpaa2_switch_fdb_get_flood_cfg(), which writes port indices
into the fixed-size cfg->if_id[DPSW_MAX_IF] array. When firmware reports
num_ifs >= 64, the loop can write past the array bounds.

Add a bound check for num_ifs in dpaa2_switch_init().

dpaa2_switch_fdb_get_flood_cfg() appends the control interface (port
num_ifs) after all matched ports. When num_ifs == DPSW_MAX_IF and all
ports match the flood filter, the loop fills all 64 slots and the control
interface write overflows by one entry.

The check uses >= because num_ifs == DPSW_MAX_IF is also functionally
broken.

build_if_id_bitmap() silently drops any ID >= 64:
      if (id[i] < DPSW_MAX_IF)
          bmap[id[i] / 64] |= ...

Fixes: 539dda3c5d19 ("staging: dpaa2-switch: properly setup switching domains")
Signed-off-by: Junrui Luo <moonafterrain@outlook.com>
Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Link: https://patch.msgid.link/SYBPR01MB78812B47B7F0470B617C408AAF74A@SYBPR01MB7881.ausprd01.prod.outlook.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>