hw/arm: allwinner: Don't enable PSCI conduit when booting guest in EL3

Change the allwinner-h3 based board to use the new boot.c
functionality to allow us to enable psci-conduit only if the guest is
being booted in EL1 or EL2, so that if the user runs guest EL3
firmware code our PSCI emulation doesn't get in its way.

To do this we stop setting the psci-conduit property on the CPU
objects in the SoC code, and instead set the psci_conduit field in
the arm_boot_info struct to tell the common boot loader code that
we'd like PSCI if the guest is starting at an EL that it makes sense
with.

This affects the orangepi-pc board.

This commit leaves the secondary CPUs in the powered-down state if
the guest is booting at EL3, which is the same behaviour as before
this commit.  The secondaries can no longer be started by that EL3
code making a PSCI call but can still be started via the CPU
Configuration Module registers (which we model in
hw/misc/allwinner-cpucfg.c).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Tested-by: Cédric Le Goater <clg@kaod.org>
Tested-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Message-id: 20220127154639.2090164-6-peter.maydell@linaro.org