mm/damon/sysfs: eliminate potential uninitialized variable warning

The "err" variable is not initialized if damon_target_has_pid(ctx) is
false and sys_target->regions->nr is zero.

Link: https://lkml.kernel.org/r/739e6aaf-a634-4e33-98a8-16546379ec9f@moroto.mountain
Fixes: 0bcd216c4741 ("mm/damon/sysfs: update monitoring target regions for online input commit")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/sysfs.c

@@ -1172,7 +1172,7 @@ static int damon_sysfs_update_target(struct damon_target *target,
 		struct damon_ctx *ctx,
 		struct damon_sysfs_target *sys_target)
 {
-	int err;
+	int err = 0;
 
 	if (damon_target_has_pid(ctx)) {
 		err = damon_sysfs_update_target_pid(target, sys_target->pid);