random: Do not include <linux/prandom.h> in <linux/random.h>

Files that use prandom infrastructure are now converted to
use <linux/prandom.h> header instead of <linux/random.h>.
Remove the legacy inclusion of <linux/prandom.h> from
<linux/random.h>.

This is the "nice cleanup" part, wished in c0842fbc.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Fixes: c0842fbc ("random32: move the pseudo-random 32-bit definitions to prandom.h")
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>