PCI/MSI: Remove unused list access in __pci_restore_msix_state()

In __pci_restore_msix_state(), we get the first element from msi_list, but
we never use it.  Remove this useless code.

Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>