Commit:

  8309f86c ("x86/tsc: Provide 'tsc=unstable' boot parameter")

added a new 'tsc=unstable' parameter, but didn't document it.

Document it.
Signed-off-by: NDou Liyang <douly.fnst@cn.fujitsu.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: <corbet@lwn.net>
Cc: <pasha.tatashin@oracle.com>
Cc: <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1507539813-11420-1-git-send-email-douly.fnst@cn.fujitsu.comSigned-off-by: NIngo Molnar <mingo@kernel.org>