x86/vLAPIC: don't leak regs page from vlapic_init() upon error

Fixes: 8a981e0bf2 ("Make map_domain_page_global fail")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

xen/arch/x86/hvm/vlapic.c

@@ -1625,6 +1625,7 @@ int vlapic_init(struct vcpu *v)
         vlapic->regs = __map_domain_page_global(vlapic->regs_page);
         if ( vlapic->regs == NULL )
         {
+            free_domheap_page(vlapic->regs_page);
             dprintk(XENLOG_ERR, "map vlapic regs error: %d/%d\n",
                     v->domain->domain_id, v->vcpu_id);
             return -ENOMEM;