octeontx2-af: npc: cn20k: Reject missing default-rule MCAM indices

octeontx2-af: npc: cn20k: Reject missing default-rule MCAM indices

When cn20k default L2 rules are not installed,
npc_cn20k_dft_rules_idx_get() leaves broadcast, multicast, promiscuous, and
unicast slots at USHRT_MAX. npc_get_nixlf_mcam_index() previously returned
that sentinel as a valid MCAM index, so callers could program hardware with
an invalid index.

Return -EINVAL from the cn20k branches of npc_get_nixlf_mcam_index() when
the requested slot is still USHRT_MAX. Harden cn20k NPC MCAM entry helpers
to reject out-of-range indices before touching hardware.

Drop the early bounds check in npc_enable_mcam_entry() for cn20k so invalid
indices are validated inside npc_cn20k_enable_mcam_entry() instead of being
silently ignored.

In rvu_npc_update_flowkey_alg_idx(), treat negative MCAM indices like
out-of-range values, and only update RSS actions for promiscuous and
all-multi paths when the resolved index is non-negative.

Cc: Suman Ghosh <sumang@marvell.com>
Fixes: 6d1e70282f76 ("octeontx2-af: npc: cn20k: Use common APIs")
Signed-off-by: Ratheesh Kannoth <rkannoth@marvell.com>
Link: https://patch.msgid.link/20260429022722.1110289-11-rkannoth@marvell.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>