bcachefs: print_str_as_lines() -> print_str()

bcachefs: print_str_as_lines() -> print_str()

bch2_print_string_as_lines() is a low level helper that allows messages
longer than 1k to be printed without truncation.

But we should always be printing with the helpers that take a filesystem
object, if we're in fsck they direct output to the userspace process
controlling fsck instead of the dmesg log.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>