octeontx2-af: Fixes static warnings

Fixes smatch static tool warning reported by smatch tool.

rvu_npc_hash.c:1232 rvu_npc_exact_del_table_entry_by_id() error:
uninitialized symbol 'drop_mcam_idx'.

rvu_npc_hash.c:1312 rvu_npc_exact_add_table_entry() error:
uninitialized symbol 'drop_mcam_idx'.

rvu_npc_hash.c:1391 rvu_npc_exact_update_table_entry() error:
uninitialized symbol 'hash_index'.

rvu_npc_hash.c:1428 rvu_npc_exact_promisc_disable() error:
uninitialized symbol 'drop_mcam_idx'.

rvu_npc_hash.c:1473 rvu_npc_exact_promisc_enable() error:
uninitialized symbol 'drop_mcam_idx'.

otx2_dmac_flt.c:191 otx2_dmacflt_update() error: 'rsp'
dereferencing possible ERR_PTR()

otx2_dmac_flt.c:60 otx2_dmacflt_add_pfmac() error: 'rsp'
dereferencing possible ERR_PTR()

Signed-off-by: Ratheesh Kannoth <rkannoth@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>