perf/x86/intel/uncore: Add BW counters for GT, IA and IO breakdown

Linux only has support to read total DDR reads and writes. Here we
add support to enable bandwidth breakdown-GT, IA and IO. Breakdown
of BW is important to debug and optimize memory access. This can also
be used for telemetry and improving the system software.The offsets for
GT, IA and IO are added and these free running counters can be accessed
via MMIO space.

The BW breakdown can be measured using the following cmd:

  perf stat -e uncore_imc/gt_requests/,uncore_imc/ia_requests/,uncore_imc/io_requests/

             30.57 MiB  uncore_imc/gt_requests/
           1346.13 MiB  uncore_imc/ia_requests/
            190.97 MiB  uncore_imc/io_requests/

       5.984572733 seconds time elapsed

     BW/s = <gt,ia,io>_requests/time elapsed

Signed-off-by: Vaibhav Shankar <vaibhav.shankar@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200814022234.23605-1-vaibhav.shankar@intel.com