Btrfs: Add error handle for btrfs_search_slot() in btrfs_read_chunk_tree()

We need to check return value of btrfs_search_slot() in
btrfs_read_chunk_tree() and do corresponding error handing.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>