drm: tweak header name

Use linux/mman.h to make sure we get all mmap flags we need.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

include/drm/drmP.h

@@ -57,8 +57,7 @@
 #include <linux/workqueue.h>
 #include <linux/dma-fence.h>
 #include <linux/module.h>
-
-#include <asm/mman.h>
+#include <linux/mman.h>
 #include <asm/pgalloc.h>
 #include <linux/uaccess.h>