x86/tsc: Print tsc_khz, when it differs from cpu_khz

If CPU and TSC frequency are the same the printout of the CPU frequency is
valid for the TSC as well:

      tsc: Detected 2900.000 MHz processor

If the TSC frequency is different there is no information in dmesg. Add a
conditional printout:

  tsc: Detected 2904.000 MHz TSC
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Link: https://lkml.kernel.org/r/537b342debcd8e8aebc8d631015dcdf9f9ba8a26.1513920414.git.len.brown@intel.com

arch/x86/kernel/tsc.c

@@ -1316,6 +1316,12 @@ void __init tsc_init(void)
 		(unsigned long)cpu_khz / 1000,
 		(unsigned long)cpu_khz % 1000);
 
+	if (cpu_khz != tsc_khz) {
+		pr_info("Detected %lu.%03lu MHz TSC",
+			(unsigned long)tsc_khz / 1000,
+			(unsigned long)tsc_khz % 1000);
+	}
+
 	/* Sanitize TSC ADJUST before cyc2ns gets initialized */
 	tsc_store_and_check_tsc_adjust(true);