octeontx2-af: npc: cn20k: Initialize default-rule index outputs up front

octeontx2-af: npc: cn20k: Initialize default-rule index outputs up front

npc_cn20k_dft_rules_idx_get() wrote USHRT_MAX into individual outputs only
on some error paths (lbk promisc lookup, VF ucast lookup, and the PF rule
walk), which could leave other caller slots stale across retries.

Set every non-NULL bcast/mcast/promisc/ucast pointer to USHRT_MAX once at
entry, then drop the duplicate assignments on failure. Successful lookups
still overwrite the relevant slot before returning.

Fixes: 09d3b7a1403f ("octeontx2-af: npc: cn20k: Allocate default MCAM indexes")
Signed-off-by: Ratheesh Kannoth <rkannoth@marvell.com>
Link: https://patch.msgid.link/20260429022722.1110289-9-rkannoth@marvell.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>