glamor: make current in prepare paths

Lots of the accel paths only make current once they start
doing someting, so a lot of them call the bail paths without
make current, which means on PRIME systems for example
we end up in the wrong context.

Add a prepare pixmap in the prepare fallback path.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90667
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-and-Tested-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Eric Anholt <eric@anholt.net>

glamor/glamor_prepare.c

@@ -45,6 +45,8 @@ glamor_prep_pixmap_box(PixmapPtr pixmap, glamor_access_t access, BoxPtr box)
     if (!GLAMOR_PIXMAP_PRIV_HAS_FBO(priv))
         return TRUE;
 
+    glamor_make_current(glamor_priv);
+
     RegionInit(&region, box, 1);
 
     /* See if it's already mapped */