d3dadapter9: Revert to old throttling limit value

Recently PIPE_CAP_MAX_FRAMES_IN_FLIGHT was changed from 2
to 1:
20909284

No driver seems to overwrite the default value.

One user reports severe regressions for some games.
For now, revert to the value 2 for nine.

Cc: "19.1" mesa-stable@lists.freedesktop.org

Signed-off-by: Axel Davy <davyaxel0@gmail.com>
(cherry picked from commit 5820ac67)