KVM: Replace ->drop_interrupt_shadow() by ->set_interrupt_shadow()

This patch replaces drop_interrupt_shadow with the more
general set_interrupt_shadow, that can either drop or raise
it, depending on its parameter.  It also adds ->get_interrupt_shadow()
for future use.

Signed-off-by: Glauber Costa <glommer@redhat.com>
CC: H. Peter Anvin <hpa@zytor.com>
CC: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3c4c327..7475b02 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3178,7 +3178,7 @@
 		kvm_run->request_interrupt_window;
 
 	if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
-		kvm_x86_ops->drop_interrupt_shadow(vcpu);
+		kvm_x86_ops->set_interrupt_shadow(vcpu, 0);
 
 	inject_irq(vcpu);