mwait-idle: add a missing __init annotation

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -983,7 +983,7 @@ static void __init bxt_idle_state_table_
  * On SKL-H (model 0x5e) disable C8 and C9 if:
  * C10 is enabled and SGX disabled
  */
-static void sklh_idle_state_table_update(void)
+static void __init sklh_idle_state_table_update(void)
 {
 	u64 msr;