drm: wrap config.h include in a ifdef KERNEL

This file can be included from userspace so wrap the config.h include.
Signed-off-by: NDavid Airlie <airlied@linux.ie>

drivers/char/drm/drm.h

@@ -38,7 +38,9 @@
 #define _DRM_H_
 
 #if defined(__linux__)
+#if defined(__KERNEL__)
 #include <linux/config.h>
+#endif
 #include <asm/ioctl.h>		/* For _IO* macros */
 #define DRM_IOCTL_NR(n)		_IOC_NR(n)
 #define DRM_IOC_VOID		_IOC_NONE