mips/boston: re-randomize rng-seed on reboot

mips/boston: re-randomize rng-seed on reboot

When the system reboots, the rng-seed that the FDT has should be
re-randomized, so that the new boot gets a new seed. Since the FDT is in
the ROM region at this point, we add a hook right after the ROM has been
added, so that we have a pointer to that copy of the FDT.

Cc: Aleksandar Rikalo <aleksandar.rikalo@syrmia.com>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Message-id: 20221025004327.568476-9-Jason@zx2c4.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>