PPC: KVM: Compile fix for qemu_notify_event

The function qemu_notify_event is defined by a header that we don't
include in the PPC KVM code. Include it to get the code building
again.

  target-ppc/kvm_ppc.c: In function 'kvmppc_timer_hack':
  target-ppc/kvm_ppc.c:26:5: error: implicit declaration of function 'qemu_notify_event' [-Werror=implicit-function-declaration]
  target-ppc/kvm_ppc.c:26:5: error: nested extern declaration of 'qemu_notify_event' [-Werror=nested-externs]

Signed-off-by: Alexander Graf <agraf@suse.de>

target-ppc/kvm_ppc.c

@@ -15,6 +15,7 @@
 #include "qemu/timer.h"
 #include "kvm_ppc.h"
 #include "sysemu/device_tree.h"
+#include "qemu/main-loop.h"
 
 #define PROC_DEVTREE_PATH "/proc/device-tree"