compositor-drm: Remove unnecessary libdrm defines

The backend begins with a series of #defines of libdrm tokens, in case
the libdrm we build against is too old.

Commit efdebbc4e8 ("configure.ac: bump libdrm requirement to 2.4.68")
did what it said on the box; since we now depend on a relatively modern
libdrm, we can get rid of most of our compatibility defines.

DRM_CAP_TIMESTAMP_MONOTONIC was added in libdrm 2.4.47 (f8f1f6e37ae2).
DRM_CLIENT_CAP_UNIVERSAL_PLANES was added in libdrm 2.4.55
(8fc62ca8ac01).
DRM_CAP_CURSOR_WIDTH and HEIGHT were added in libdrm 2.4.68
(cc9a53f076d4).

Remove these four fallback definitions.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Derek Foreman <derek.foreman.samsung@gmail.com>

libweston/compositor-drm.c

@@ -65,26 +65,10 @@
 #include "linux-dmabuf.h"
 #include "linux-dmabuf-unstable-v1-server-protocol.h"
 
-#ifndef DRM_CAP_TIMESTAMP_MONOTONIC
-#define DRM_CAP_TIMESTAMP_MONOTONIC 0x6
-#endif
-
-#ifndef DRM_CLIENT_CAP_UNIVERSAL_PLANES
-#define DRM_CLIENT_CAP_UNIVERSAL_PLANES 2
-#endif
-
 #ifndef DRM_CLIENT_CAP_ASPECT_RATIO
 #define DRM_CLIENT_CAP_ASPECT_RATIO	4
 #endif
 
-#ifndef DRM_CAP_CURSOR_WIDTH
-#define DRM_CAP_CURSOR_WIDTH 0x8
-#endif
-
-#ifndef DRM_CAP_CURSOR_HEIGHT
-#define DRM_CAP_CURSOR_HEIGHT 0x9
-#endif
-
 #ifndef GBM_BO_USE_CURSOR
 #define GBM_BO_USE_CURSOR GBM_BO_USE_CURSOR_64X64
 #endif