xive/p9: Introduce XIVE_ESB_SIZE
xive/p9: Introduce XIVE_ESB_SIZE

Replace 0x20000 with a clear define.

Signed-off-by: Cédric Le Goater <2d8cace2254d4e43578d21933db015d84bcc468a@kaod.org>
Signed-off-by: Oliver O'Halloran <3dfaff8fa6ae977f042064a112a6aac576279b9b@gmail.com>

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