drm/lib: Include <linux/prandom.h> instead of <linux/random.h>

Substitute the inclusion of <linux/random.h> header with
<linux/prandom.h> to allow the removal of legacy inclusion
of <linux/prandom.h> from <linux/random.h>.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Author: ubizjak

drivers/gpu/drm/lib/drm_random.h

@@ -6,7 +6,7 @@
  * be transposed to lib/ at the earliest convenience.
  */
 
-#include <linux/random.h>
+#include <linux/prandom.h>
 
 #define DRM_RND_STATE_INITIALIZER(seed__) ({				\
 	struct rnd_state state__;					\