[PATCH 5.15.y] KVM: arm64: vgic-its: Don't dereference a NULL collection on ITT save

[Sasha Levin]

> MAPC with V=0 drops ite->collection but leaves the ITE on the device's
> ITT list, and vgic_its_save_ite() dereferences it unconditionally. A
> guest that issues MAPD, MAPTI and then MAPC(V=0) therefore oopses the
> host when the VMM issues KVM_DEV_ARM_ITS_SAVE_TABLES to migrate it.

Queued for 5.15, thanks.

-- 
Thanks,
Sasha