bcachefs: Fix missing spaces in journal_entry_dev_usage_to_text

Fixed missing spaces displayed in journal_entry_dev_usage_to_text
while adjusting the display format to improve readability.

before:
```
 # bcachefs list_journal -a -t alloc:1:0 /dev/sdb
 ...
     dev_usage: dev=0free: buckets=233180 sectors=0 fragmented=0sb: buckets=13 sectors=6152 fragmented=504journal: buckets=1847 sectors=945664 fragmented=0btree: buckets=20 sectors=10240 fragmented=0user: buckets=1419 sectors=726513 fragmented=15cached: buckets=0 sectors=0 fragmented=0parity: buckets=0 sectors=0 fragmented=0stripe: buckets=0 sectors=0 fragmented=0need_gc_gens: buckets=0 sectors=0 fragmented=0need_discard: buckets=1 sectors=0 fragmented=0
```

after:
```
 # bcachefs list_journal -a -t alloc:1:0 /dev/sdb
 ...
     dev_usage: dev=0
       free: buckets=233180 sectors=0 fragmented=0
       sb: buckets=13 sectors=6152 fragmented=504
       journal: buckets=1847 sectors=945664 fragmented=0
       btree: buckets=20 sectors=10240 fragmented=0
       user: buckets=1419 sectors=726513 fragmented=15
       cached: buckets=0 sectors=0 fragmented=0
       parity: buckets=0 sectors=0 fragmented=0
       stripe: buckets=0 sectors=0 fragmented=0
       need_gc_gens: buckets=0 sectors=0 fragmented=0
       need_discard: buckets=1 sectors=0 fragmented=0
```
Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/journal_io.c

@@ -724,13 +724,16 @@ static void journal_entry_dev_usage_to_text(struct printbuf *out, struct bch_fs
 
 	prt_printf(out, "dev=%u", le32_to_cpu(u->dev));
 
+	printbuf_indent_add(out, 2);
 	for (i = 0; i < nr_types; i++) {
+		prt_newline(out);
 		bch2_prt_data_type(out, i);
 		prt_printf(out, ": buckets=%llu sectors=%llu fragmented=%llu",
 		       le64_to_cpu(u->d[i].buckets),
 		       le64_to_cpu(u->d[i].sectors),
 		       le64_to_cpu(u->d[i].fragmented));
 	}
+	printbuf_indent_sub(out, 2);
 }
 
 static int journal_entry_log_validate(struct bch_fs *c,