btrfs: remove colon from messages with state

The message format in syslog is usually made of two parts:

  prefix ":" message

Various tools parse the prefix up to the first ":". When there's
an additional status of a btrfs filesystem like

  [5.199782] BTRFS info (device nvme1n1p1: state M): use zstd compression, level 9

where 'M' is for remount, there's one more ":" that does not conform to
the format. Remove it.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>