gallium/trace: remove useless NULL check from trace_screen_create()

Currently every target makes sure that the screen is non-null prior to
using the debug (trace including) wrappers. If that no longer holds true
we want to know and fix this ASAP rather than silently bailing out.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Acked-by: Rob Clark <robclark@freedesktop.org>

src/gallium/drivers/trace/tr_screen.c

@@ -456,9 +456,6 @@ trace_screen_create(struct pipe_screen *screen)
 {
    struct trace_screen *tr_scr;
 
-   if(!screen)
-      goto error1;
-
    if (!trace_enabled())
       goto error1;