ACPI / LPIT: Export lpit_read_residency_count_address()

Export lpit_read_residency_count_address(), so that it can be used from
drivers built as module. With the recent changes, the builtin_pci
functionality of the intel_pmc_core driver is removed and now it can be
built as a module to read this exported interface to calculate the PMC base
address.

Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Len Brown <lenb@kernel.org>
Cc: linux-acpi@vger.kernel.org

Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Tested-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@intel.com>
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>