CI: Update centos8 runs with P8 and P9 mambo
CI: Update centos8 runs with P8 and P9 mambo

Signed-off-by: Cédric Le Goater <2d8cace2254d4e43578d21933db015d84bcc468a@kaod.org>

legoater/skiboot,open-power/skiboot,qemu/skiboot,shenki/skiboot,shenki/skiboot,qemu/skiboot,shenki/skiboot,shenki/skiboot,qemu/skiboot,open-power/skiboot,open-power/skiboot,qemu/skiboot,legoater/skiboot,legoater/skiboot,legoater/skiboot,legoater/skiboot,qemu/skiboot,open-power/skiboot,open-power/skiboot,shenki/skiboot