Fix a typo in struct pcie_link_state.

The "sibiling" field in the struct pcie_link_state should be
"sibling".
Acked-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NKenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>