PCI: Update mmap-related #ifdef comments

PCI: Update mmap-related #ifdef comments

87900a7f92ae ("PCI: Add pci_mmap_resource_range() and use it for ARM64")
changed the #ifdef condition around pci_create_resource_files(),
pci_remove_resource_files(), and related functions, but did not update
comments at the #else and #ifdef.

Update the comments to match the #ifdef.

[bhelgaas: commit log, drop #endif comment since it's close to the #else]
Link: https://lore.kernel.org/r/20200821155121.nzxjeeoze4h5pone@amazon.com
Signed-off-by: Clint Sbisa <csbisa@amazon.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>