Revert "uuid: use prandom_bytes()"

This reverts commit 2a7c303dc2f3c2b7f7d9272af50e2c0e75d06c5b.
Revert "prandom: introduce prandom_bytes() and prandom_bytes_state()"

This reverts commit cea376521d56a05153cdfc94423ce024199cd723.
Revert "ext4: use prandom_u32() instead of get_random_bytes()"

This reverts commit 3bab97e087f3879d28d5a133973df33dbaf4eea7.