haiku/winsys: fix dt prototype args

Add the missing front_private, introduced with earlier commit.

(cherry picked from commit 62e27170a7f7a90091b4121002b7ce209ac7ccb0)
Fixes: 2b676570960 ("gallium/swrast: fix front buffer blitting. (v2)")
Nominated-by: Emil Velikov <emil.velikov@collabora.com>
[Emil Velikov: add commit message, fixes tag]
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
1 file changed