alpha/PCI: Use BAR index in sysfs attr->private instead of resource pointer

alpha/PCI: Use BAR index in sysfs attr->private instead of resource pointer

Currently, Alpha's pci_create_one_attr() stores a resource pointer in
attr->private, and pci_mmap_resource() loops through all BARs to find
the matching index.

Store the BAR index directly in attr->private and retrieve the resource via
pci_resource_n().  This eliminates the loop and aligns with the convention
used by the generic PCI sysfs code.

The PCI core change was first added in the commit dca40b186b75 ("PCI: Use
BAR index in sysfs attr->private instead of resource pointer").

Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Magnus Lindholm <linmag7@gmail.com>
Tested-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Acked-by: Magnus Lindholm <linmag7@gmail.com>
Link: https://patch.msgid.link/20260508043543.217179-13-kwilczynski@kernel.org