Retire Rml full PV search at depth == 1

Retire Rml full PV search at depth == 1

Now that Rml ordering is based on normal MovePicker logic,
apart for the ttMove that is given, we can avoid to score
all the root moves at depth 1. We only need it for easy move
detection logic, but in this case we just need to score the
first two best moves and not all the Rml set.

No regression after 6400 games
Mod vs Orig 1052 1012 4336 ELO +2 (+- 4.9)

Signed-off-by: Marco Costalba <mcostalba@gmail.com>