x86/tsc: Mark cyc2ns_init() and detect_art() __init

x86/tsc: Mark cyc2ns_init() and detect_art() __init

These two functions are only called by tsc_init(), which is an __init
function during boot time, so mark them __init as well.

Signed-off-by: Dou Liyang <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>