KVM: PPC: Book3S HV: remove unnecessary casts

Remove unnecessary casts, from "void *" to "struct kvmppc_xics *"

Signed-off-by: Nour-eddine Taleb <kernel.noureddine@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220303143416.201851-1-kernel.noureddine@gmail.com