x86, tsc: fix section mismatch warning

WARNING: vmlinux.o(.text+0x7950): Section mismatch in reference from the function native_calibrate_tsc() to the function .init.text:tsc_read_refs()
The function native_calibrate_tsc() references
the function __init tsc_read_refs().
This is often because native_calibrate_tsc lacks a __init
annotation or the annotation of tsc_read_refs is wrong.

tsc_read_refs is called from native_calibrate_tsc which is not __init
and native_calibrate_tsc cannot be marked __init

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/kernel/tsc.c

@@ -104,7 +104,7 @@ __setup("notsc", notsc_setup);
 /*
  * Read TSC and the reference counters. Take care of SMI disturbance
  */
-static u64 __init tsc_read_refs(u64 *pm, u64 *hpet)
+static u64 tsc_read_refs(u64 *pm, u64 *hpet)
 {
 	u64 t1, t2;
 	int i;