KVM: PPC: Book3S PR: Remove unused variable

This fixes a compile error with W=1.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210819125656.14498-5-clg@kaod.org