drm: Untangle __KERNEL__ guards

make headers_install can't handle fancy conditions, so let's simplify
things for it a bit.

Cc: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459348943-12803-1-git-send-email-daniel.vetter@ffwll.ch

include/uapi/drm/drm.h

@@ -36,7 +36,13 @@
 #ifndef _DRM_H_
 #define _DRM_H_
 
-#if defined(__KERNEL__) || defined(__linux__)
+#if defined(__KERNEL__)
+
+#include <linux/types.h>
+#include <asm/ioctl.h>
+typedef unsigned int drm_handle_t;
+
+#elif defined(__linux__)
 
 #include <linux/types.h>
 #include <asm/ioctl.h>