perf tools: Allow to use cpuinfo on LoongArch

Define these macros so that the CPU name can be displayed when running
'perf report' and 'perf timechart'.

Committer notes:

No need to have:

	if (strcasestr(buf, "Model Name")) {
		strlcpy(cpu_m, &buf[13], 255);
		break;
	} else if (strcasestr(buf, "model name")) {
		strlcpy(cpu_m, &buf[13], 255);
		break;
	}

As the point of strcasestr() is to be case insensitive to both the
haystack and the needle, so simplify the above to just:

	if (strcasestr(buf, "model name")) {
		strlcpy(cpu_m, &buf[13], 255);
		break;
	}

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Acked-by: Huacai Chen <chenhuacai@loongson.cn>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: loongarch@lists.linux.dev
Cc: loongson-kernel@lists.loongnix.cn
Link: https://lore.kernel.org/r/db968a186a10e4629fe10c26a1210f7126ad41ec.1692962043.git.siyanteng@loongson.cn


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>