PCI: Fix PCI kconfig menu organization

After commit eb01d42a ("PCI: consolidate PCI config entry in
drivers/pci"), all the PCI kconfig options appear below "PCI support"
rather than within a sub-menu.  This is because menuconfig expects all
kconfig entries to be enclosed in an if/endif section.  Add the missing
if/endif.

With this, "depends on PCI" is redundant in the sub-menu  entries and can
be removed.

Fixes: eb01d42a ("PCI: consolidate PCI config entry in drivers/pci")
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>