ARM: KVM: Add HYP mode entry code

This part is almost entierely borrowed from the existing code, just
slightly simplifying the HYP function call (as we now save SPSR_hyp
in the world switch).

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
diff --git a/arch/arm/kvm/hyp/hyp.h b/arch/arm/kvm/hyp/hyp.h
index 8b1156b..8b9c2eb 100644
--- a/arch/arm/kvm/hyp/hyp.h
+++ b/arch/arm/kvm/hyp/hyp.h
@@ -123,4 +123,6 @@
 
 int asmlinkage __guest_enter(struct kvm_vcpu *vcpu,
 			     struct kvm_cpu_context *host);
+int asmlinkage __hyp_do_panic(const char *, int, u32);
+
 #endif /* __ARM_KVM_HYP_H__ */