KVM: PPC: Book3s: Fix warning about xics_rm_h_xirr_x

This fixes "no previous prototype":

arch/powerpc/kvm/book3s_hv_rm_xics.c:482:15:
warning: no previous prototype for 'xics_rm_h_xirr_x' [-Wmissing-prototypes]

Reported by the kernel test robot.

Fixes: b22af904 ("KVM: PPC: Book3s: Remove real mode interrupt controller hcalls handlers")
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220622055235.1139204-1-aik@ozlabs.ru

arch/powerpc/kvm/book3s_xics.h

@@ -143,6 +143,7 @@ static inline struct kvmppc_ics *kvmppc_xics_find_ics(struct kvmppc_xics *xics,
 }
 
 extern unsigned long xics_rm_h_xirr(struct kvm_vcpu *vcpu);
+extern unsigned long xics_rm_h_xirr_x(struct kvm_vcpu *vcpu);
 extern int xics_rm_h_ipi(struct kvm_vcpu *vcpu, unsigned long server,
 			 unsigned long mfrr);
 extern int xics_rm_h_cppr(struct kvm_vcpu *vcpu, unsigned long cppr);