x86/tsc: Fix broken CONFIG_X86_TSC=n build

Add the missing return statement to the inline stub
tsc_store_and_check_tsc_adjust() and add the other stubs to make a
SMP=y,TSC=n build happy.

While at it, remove the unused variable from the UP variant of
tsc_store_and_check_tsc_adjust().

Fixes: commit ba75fb646931 ("x86/tsc: Sync test only for the first cpu in a package")
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/include/asm/tsc.h

@@ -45,15 +45,16 @@ extern int tsc_clocksource_reliable;
  * Boot-time check whether the TSCs are synchronized across
  * all CPUs/cores:
  */
-extern void check_tsc_sync_source(int cpu);
-extern void check_tsc_sync_target(void);
-
 #ifdef CONFIG_X86_TSC
 extern bool tsc_store_and_check_tsc_adjust(void);
 extern void tsc_verify_tsc_adjust(void);
+extern void check_tsc_sync_source(int cpu);
+extern void check_tsc_sync_target(void);
 #else
-static inline bool tsc_store_and_check_tsc_adjust(void) { }
+static inline bool tsc_store_and_check_tsc_adjust(void) { return false; }
 static inline void tsc_verify_tsc_adjust(void) { }
+static inline void check_tsc_sync_source(int cpu) { }
+static inline void check_tsc_sync_target(void) { }
 #endif
 
 extern int notsc_setup(char *);

arch/x86/kernel/tsc_sync.c

@@ -61,7 +61,7 @@ void tsc_verify_tsc_adjust(void)
 #ifndef CONFIG_SMP
 bool __init tsc_store_and_check_tsc_adjust(void)
 {
-	struct tsc_adjust *ref, *cur = this_cpu_ptr(&tsc_adjust);
+	struct tsc_adjust *cur = this_cpu_ptr(&tsc_adjust);
 	s64 bootval;
 
 	if (!boot_cpu_has(X86_FEATURE_TSC_ADJUST))