x86/HVM: move evtchn_upcall_vector field

... into an available 8-bit slot, rather than having it followed by 7
bytes of padding.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

xen/arch/x86/include/asm/hvm/vcpu.h

@@ -129,6 +129,8 @@ struct hvm_vcpu {
     spinlock_t          tm_lock;
     struct list_head    tm_list;
 
+    uint8_t             evtchn_upcall_vector;
+
     bool                flag_dr_dirty;
     bool                debug_state_latch;
     bool                single_step;
@@ -165,8 +167,6 @@ struct hvm_vcpu {
     /* In mode delay_for_missed_ticks, VCPUs have differing guest times. */
     int64_t             stime_offset;
 
-    u8                  evtchn_upcall_vector;
-
     struct hvm_vcpu_io  hvm_io;
 
     /* Pending hw/sw interrupt (.vector = -1 means nothing pending). */