mm/damon/vaddr: use pr_debug() for damon_va_three_regions() failure logging

Failure of 'damon_va_three_regions()' is logged using 'pr_err()'.  But,
the function can fail in legal situations.  To avoid making users be
surprised and to keep the kernel clean, this makes the log to be printed
using 'pr_debug()'.

Link: https://lkml.kernel.org/r/20211229131016.23641-3-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/damon/vaddr.c

@@ -238,7 +238,7 @@ static void __damon_va_init_regions(struct damon_ctx *ctx,
 	int i;
 
 	if (damon_va_three_regions(t, regions)) {
-		pr_err("Failed to get three regions of target %lu\n", t->id);
+		pr_debug("Failed to get three regions of target %lu\n", t->id);
 		return;
 	}