device-tree: add re-randomization helper function

device-tree: add re-randomization helper function

When the system reboots, the rng-seed that the FDT has should be
re-randomized, so that the new boot gets a new seed. Several
architectures require this functionality, so export a function for
injecting a new seed into the given FDT.

Cc: Alistair Francis <alistair.francis@wdc.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20221025004327.568476-3-Jason@zx2c4.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>