tools/zynqmp_pm_cfg_obj_convert.py: fix build with Vivado 2021.x

This tool fails with a pm_cfg_obj.c file generated by Vitis 2021.2. This is
because that version of Vitis added the PM_CONFIG_OBJECT_TYPE_BASE that was
not previously generated, thus the script does not implement it.

Reported-by: Neal Frager <nealf@xilinx.com>
[report: https://lists.buildroot.org/pipermail/buildroot/2022-February/636639.html

]
Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Link: https://lore.kernel.org/r/20220212125121.3398547-1-luca@lucaceresoli.net


Signed-off-by: Michal Simek <michal.simek@xilinx.com>