amd8111e: use pdev->pm_cap instead of pci_find_capability(.., PCI_CAP_ID_PM)

Pci core has been saved pm cap register offset by pdev->pm_cap in pci_pm_init()
in init path. So we can use pdev->pm_cap instead of using
pci_find_capability(pdev, PCI_CAP_ID_PM) for better performance and simplified code.

Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Bill Pemberton <wfp5p@virginia.edu>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: netdev@vger.kernel.org (open list:NETWORKING DRIVERS)
Signed-off-by: David S. Miller <davem@davemloft.net>