x86/hpet: Sanitize stub functions

Mark them inline and remove the pointless 'return;' statement.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Link: https://lkml.kernel.org/r/20190623132434.754768274@linutronix.de

arch/x86/kernel/hpet.c

@@ -692,16 +692,10 @@ static int hpet_cpuhp_dead(unsigned int cpu)
 }
 #else
 
-static void hpet_msi_capability_lookup(unsigned int start_timer)
-{
-	return;
-}
+static inline void hpet_msi_capability_lookup(unsigned int start_timer) { }
 
 #ifdef CONFIG_HPET
-static void hpet_reserve_msi_timers(struct hpet_data *hd)
-{
-	return;
-}
+static inline void hpet_reserve_msi_timers(struct hpet_data *hd) { }
 #endif
 
 #define hpet_cpuhp_online	NULL
@@ -820,7 +814,7 @@ static struct clocksource clocksource_hpet = {
 	.resume		= hpet_resume_counter,
 };
 
-static int hpet_clocksource_register(void)
+static int __init hpet_clocksource_register(void)
 {
 	u64 start, now;
 	u64 t1;