KVM: fix sparse warnings: context imbalance

Impact: Attribute function with __acquires(...) resp. __releases(...).

Fix this sparse warnings:
  arch/x86/kvm/i8259.c:34:13: warning: context imbalance in 'pic_lock' - wrong count at exit
  arch/x86/kvm/i8259.c:39:13: warning: context imbalance in 'pic_unlock' - unexpected unlock
Signed-off-by: NHannes Eder <hannes@hanneseder.net>
Signed-off-by: NAvi Kivity <avi@redhat.com>

arch/x86/kvm/i8259.c

@@ -32,11 +32,13 @@
 #include <linux/kvm_host.h>
 
 static void pic_lock(struct kvm_pic *s)
+	__acquires(&s->lock)
 {
 	spin_lock(&s->lock);
 }
 
 static void pic_unlock(struct kvm_pic *s)
+	__releases(&s->lock)
 {
 	struct kvm *kvm = s->kvm;
 	unsigned acks = s->pending_acks;