octeontx2-af: initialize action variable

Clang static analysis reports this representative issue
rvu_npc.c:898:15: warning: Assigned value is garbage
  or undefined
  req.match_id = action.match_id;
               ^ ~~~~~~~~~~~~~~~

The initial setting of action is conditional on
 if (is_mcam_entry_enabled(...))
The later check of action.op will sometimes be garbage.
So initialize action.

Reduce setting of
  *(u64 *)&action = 0x00;
to
  *(u64 *)&action = 0;

Fixes: 967db352 ("octeontx2-af: add support for multicast/promisc packet replication feature")
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>