PCI: remove redundant checking in PCI Express capability routines

There are a number of redundant pci_is_pcie() checks in various PCI
Express capabilities related routines like the following:

    if (!pci_is_pcie(dev))
	return false;

    pos = pci_pcie_cap(dev);
    if (!pos)
	return false;

The current pci_is_pcie() implementation is merely:

    static inline bool pci_is_pcie(struct pci_dev *dev)
    {
        return !!pci_pcie_cap(dev);
    }

so we can just drop the pci_is_pcie() test in such cases.

Acked-by: Donald Dutile <ddutile@redhat.com>
Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>