net, lib/once: remove {net_}get_random_once_wait macro

DO_ONCE(func, ...) will call func with spinlock which acquired by
spin_lock_irqsave in __do_once_start.  But the get_random_once_wait will
sleep in get_random_bytes_wait -> wait_for_random_bytes.

Fortunately, there is no place to use {net_}get_random_once_wait, so we
could remove them simply.

Link: https://lkml.kernel.org/r/20220619074641.40916-1-wuchi.zero@gmail.com
Signed-off-by: wuchi <wuchi.zero@gmail.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>