st/nine: Default thread_submit to true

When rendering fullscreen with vsync on at
a rate close to the refresh rate, you can
miss pageflips by submitting buffers for pageflip
that end up not finished being rendered when the pageflip is due.

With Nine in this situation you could get half the refresh
rate fps before this patch.

Due to the way the presentation backend is implemented,
it's not possible to easily detect the situation and adapt (use
one more backbuffer, but only in this scenario to not increase input
lap when the issue is not present).

thread_submit doesn't have this issue.

Let's default thread_submit to true.

Signed-off-by: Axel Davy <davyaxel0@gmail.com>
Acked-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10160>

src/gallium/targets/d3dadapter9/drm.c

@@ -54,7 +54,7 @@ const driOptionDescription __driConfigOptionsNine[] = {
     DRI_CONF_SECTION_NINE
         DRI_CONF_NINE_OVERRIDEVENDOR(-1)
         DRI_CONF_NINE_THROTTLE(-2)
-        DRI_CONF_NINE_THREADSUBMIT(false)
+        DRI_CONF_NINE_THREADSUBMIT(true)
         DRI_CONF_NINE_ALLOWDISCARDDELAYEDRELEASE(true)
         DRI_CONF_NINE_TEARFREEDISCARD(false)
         DRI_CONF_NINE_CSMT(-1)