perf/x86/intel/uncore: Factor out box ref/unref functions

For uncore box which can only be accessed by MSR, its reference
box->refcnt is updated in CPU hot plug. The uncore boxes need to be
initalized and exited accordingly for the first/last CPU of a socket.

Starts from Snow Ridge server, a new type of uncore box is introduced,
which can only be accessed by MMIO. The driver needs to map/unmap
MMIO space for the first/last CPU of a socket.

Extract the codes of box ref/unref and init/exit for reuse later.

There is no functional change.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@kernel.org
Cc: eranian@google.com
Link: https://lkml.kernel.org/r/1556672028-119221-4-git-send-email-kan.liang@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>