Initialize hv_clock to zero

This stops callers from getting random values if data is accessed before
clock is initialized; instead they will get zeroed clock values (because
computation involves a multiplication by a factor in hv_clock).

Signed-off-by: Zachary Amsden <zamsden@redhat.com>

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index eb9b76c..e7acd0d 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -40,7 +40,7 @@ static int parse_no_kvmclock(char *arg)
 early_param("no-kvmclock", parse_no_kvmclock);
 
 /* The hypervisor will put information about time periodically here */
-static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock) = {0};
 static struct pvclock_wall_clock wall_clock;
 
 /*