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 <[e-mail]>
Cc: Maarten Lankhorst <[e-mail]>
Cc: Maxime Ripard <[e-mail]>
Cc: Thomas Zimmermann <[e-mail]>
Cc: David Airlie <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Signed-off-by: Jason A. Donenfeld <[e-mail]>

drivers/gpu/drm/lib/drm_random.h

···
  * 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__;					\