perf c2c: Add helpers to get counts of loads or stores

perf c2c: Add helpers to get counts of loads or stores

Wrap repeated code in helper functions get_load_llc_misses,
get_load_cache_hits. For consistence, helper function get_stores is
wraped as well.

Reviewed-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220906032906.21395-3-shangxiaojing@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>