arch/sh: pci: don't use disabled resources

In pcibios_scanbus(), we provide to the PCI core the usable MEM and IO
regions using pci_add_resource_offset(). We travel through all
resources available in the "struct pci_channel".

Also, in register_pci_controller(), we travel through all resources to
request them, making sure they don't conflict with already requested
resources.

However, some resources may be disabled, in which case they should not
be requested nor provided to the PCI core.

In the current situation, none of the resources are disabled. However,
follow-up patches in this series will make some resources disabled,
making this preliminary change necessary.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Rich Felker <dalias@libc.org>