bcache: Convert to use sysfs_emit()/sysfs_emit_at() APIs

Follow the advice of the Documentation/filesystems/sysfs.rst and show()
should only use sysfs_emit() or sysfs_emit_at() when formatting the
value to be returned to user space.
Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn>
Signed-off-by: Coly Li <colyli@suse.de>
Link: https://lore.kernel.org/r/20230615121223.22502-2-colyli@suse.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/bcache/sysfs.c

@@ -1111,7 +1111,7 @@ SHOW(__bch_cache)
 
 		vfree(p);
 
-		ret = scnprintf(buf, PAGE_SIZE,
+		ret = sysfs_emit(buf,
 				 "Unused:		%zu%%\n"
 				 "Clean:		%zu%%\n"
 				 "Dirty:		%zu%%\n"
@@ -1126,11 +1126,10 @@ SHOW(__bch_cache)
 				 n * ca->sb.bucket_size / (ARRAY_SIZE(q) + 1));
 
 		for (i = 0; i < ARRAY_SIZE(q); i++)
-			ret += scnprintf(buf + ret, PAGE_SIZE - ret,
-					 "%u ", q[i]);
+			ret += sysfs_emit_at(buf, ret, "%u ", q[i]);
 		ret--;
 
-		ret += scnprintf(buf + ret, PAGE_SIZE - ret, "]\n");
+		ret += sysfs_emit_at(buf, ret, "]\n");
 
 		return ret;
 	}