8xx: Optimize TLB Miss handlers

Only update pte w.r.t ACCESSED if it isn't already set
Wrap ACCESSED with #ifndef NO_SWAP for too ease optimization.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: Willy Tarreau <w@1wt.eu>