x86/hpet: fix cpumask allocation after 23990:1c8789852eaf

hpet_fsb_cap_lookup(), if it doesn't find any FSB capable timer, leaves
hpet_events allocated, while hpet_events->cpumask may not have been, As
we're pretty generous with these one-time allocations already (in that
hpet_events doesn't get freed when no usable counters were found, even
if in that case only the first array entry [or none at all] may get
used), simply make the cpumask allocation in the legacy case
independent of whether hpet_events was NULL before.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/hpet.c
+++ b/xen/arch/x86/hpet.c
@@ -512,15 +512,8 @@ void __init hpet_broadcast_init(void)
             return;
 
         if ( !hpet_events )
-        {
             hpet_events = xzalloc(struct hpet_event_channel);
-            if ( hpet_events && !zalloc_cpumask_var(&hpet_events->cpumask) )
-            {
-                xfree(hpet_events);
-                hpet_events = NULL;
-            }
-        }
-        if ( !hpet_events )
+        if ( !hpet_events || !zalloc_cpumask_var(&hpet_events->cpumask) )
             return;
         hpet_events->irq = -1;