platform: starfive: return error if needed devices are not present

Jh7110's reset driver needs power management device and clock controller
device to work. Currently, the driver proceed anyway without these
devices, and invalid addresses (jh7110_inst.pmu_reg_base and
jh7110_inst.clk_reg_base) are used during reboot, which causes
unpredictable broken behaviors.

If these devices are not present, return -SBI_ENODEV.

Signed-off-by: Nam Cao <namcao@linutronix.de>
Tested-by: Minda Chen <minda.chen@starfivetech.com>
Reviewed-by: Anup Patel <anup@brainfault.org>