configs/zynqmp_*: move to external Bootlin stable toolchain
This moves the zynqmp defconfigs to the Bootlin glibc stable external toolchain
as per[1].
[1]: https://elinux.org/Buildroot:DeveloperDaysELCE2024#Rules_for_defconfigs
This patch has been run-tested on the zcu106 evaluation board.
This patch has been run-tested on the kv260 starter kit.
Signed-off-by: Neal Frager <neal.frager@amd.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>