Include xf86drm.h instead of sarea.h

Fixes build against current xorg-x11-server-devel from Fedora
34/35/rawhide.
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

src/drmmode_display.c

@@ -40,7 +40,7 @@
 #include "mipointrst.h"
 #include "xf86cmap.h"
 #include "xf86Priv.h"
-#include "sarea.h"
+#include <xf86drm.h>
 
 #include "drmmode_display.h"
 #include "amdgpu_bo_helper.h"