Currently we only update the sysfs event files per available MSR, we
didn't actually disallow creating unlisted events.

Rework things such that the dectection, sysfs listing and event
creation are better coordinated.

Sadly it appears it's impossible to probe R/O MSRs under virt. This
means we have to do the full model table to avoid listing all MSRs all
the time.
Tested-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>