btrfs/174: Adjust error message when setting compressed flag

btrfs/174: Adjust error message when setting compressed flag

Following kernel commit "btrfs: add missing check for nocow and
compression inode flags" btrfs refuses setting +c on +C files during
validation of the args. Account for this by adjusting the expected
error message.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>