drm: fix inclusion of drm.h in savage_drm.h

Using `#include "drm.h"` instead of `#include <drm/drm.h>` allow drm
headers to be moved in another directory without changes, like for the
libdrm imports.
Signed-off-by: Gabriel Laskar <gabriel@lse.epita.fr>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
CC: Emil Velikov <emil.l.velikov@gmail.com>
CC: Mikko Rapeli <mikko.rapeli@iki.fi>

include/uapi/drm/savage_drm.h

@@ -26,7 +26,7 @@
 #ifndef __SAVAGE_DRM_H__
 #define __SAVAGE_DRM_H__
 
-#include <drm/drm.h>
+#include "drm.h"
 
 #ifndef __SAVAGE_SAREA_DEFINES__
 #define __SAVAGE_SAREA_DEFINES__