perf tools: Do not remove addr_location.thread in thread__find_map()

The thread__find_map() is to find a map for a given address in the
given thread's address space. It searches maps based on the cpu mode
and fills various information in the addr_location data structure.

It might change al->maps and al->map, but not al->thread. Then I
think no reason to not set the al->thread at the beginning.

Also get rid of the duplicate 'al->map = NULL' part.

Fixes: 0dd5041c9a0ea ("perf addr_location: Add init/exit/copy functions")
Acked-by: Ian Rogers <[e-mail]>
Acked-by: James Clark <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Suzuki K Poulose <[e-mail]>
Cc: Mike Leach <[e-mail]>
Cc: Leo Yan <[e-mail]>
Cc: John Garry <[e-mail]>
Cc: Will Deacon <[e-mail]>
Signed-off-by: Namhyung Kim <[e-mail]>

tools/perf/util/event.c

···
 	maps__zput(al->maps);
 	map__zput(al->map);
 	thread__zput(al->thread);
+	al->thread = thread__get(thread);
 
 	al->addr = addr;
 	al->cpumode = cpumode;
 	al->filtered = 0;
 
-	if (machine == NULL) {
-		al->map = NULL;
+	if (machine == NULL)
 		return NULL;
-	}
 
 	if (cpumode == PERF_RECORD_MISC_KERNEL && perf_host) {
 		al->level = 'k';
···
 		al->level = 'u';
 	} else {
 		al->level = 'H';
-		al->map = NULL;
 
 		if ((cpumode == PERF_RECORD_MISC_GUEST_USER ||
 			cpumode == PERF_RECORD_MISC_GUEST_KERNEL) &&
···
 		return NULL;
 	}
 	al->maps = maps__get(maps);
-	al->thread = thread__get(thread);
 	al->map = map__get(maps__find(maps, al->addr));
 	if (al->map != NULL) {
 		/*