perf/x86/intel/uncore: Add infrastructure for free running counters

There are a number of free running counters introduced for uncore, which
provide highly valuable information to a wide array of customers.
However, the generic uncore code doesn't support them yet.

The free running counters will be specially handled based on their
unique attributes:

 - They are read-only. They cannot be enabled/disabled.

 - The event and the counter are always 1:1 mapped. It doesn't need to
   be assigned nor tracked by event_list.

 - They are always active. It doesn't need to check the availability.

 - They have different bit width.

Also, using inline helpers to replace the check for fixed counter and
free running counter.

Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: acme@kernel.org
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/1525371913-10597-5-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>