btrfs-progs: print root dir verbose error in fsck

Before this patch, when btrfsck found an error in root dir, it will only
output the following message "root %llu root dir %llu error" without any
detailed error.

Just add print_inode_error() to print out the whole error.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>