KVM: VMX: clean up pi_wakeup_handler

Passing per_cpu() to list_for_each_entry() causes the macro to be
evaluated N+1 times for N sleeping vCPUs.  This is a very small
inefficiency, and the code is cleaner if the address of the per-CPU
variable is loaded earlier.  Do this for both the list and the spinlock.

Signed-off-by: Li RongQing <lirongqing@baidu.com>
Message-Id: <1649244302-6777-1-git-send-email-lirongqing@baidu.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>