iris: INTEL performance query implementation

iris: INTEL performance query implementation

low-level implementation of INTEL-performance-query APIs in
Intel iris driver. Most of functions and procedures defined here
are adopted from i965 driver (brw_performance_query.c)

v2: - replace genX_init_performance_query with
      iris_init_perfquery_functions which is gen's version agnositic
    - general code clean-up

v3: include gen_perf_gens.h as some of defines were moved to this new
    header file

v4: - checking for kernel 4.13+ won't be needed here as Iris won't be
      loaded anyway without DRM_SYNCOBJ that is enabled after Kernel
      4.13.

    - checking whether gen < 8 or is_cherryview won't be required as
      well because those cases are screened in iris_screen_create.

v5: remove genX(init_performance_query)

v6: - remove oa_metrics_kernel_support as iris works only with kernel
    4.18 and newer.

    - use perf functions defined in separate file, iris_perf.h/c

Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>