PCI/ACPI: move _OSC code to pci_root.c

Move PCI _OSC management code from drivers/pci/pci-acpi.c to
drivers/acpi/pci_root.c. The benefits are

- We no longer need struct osc_data and its management code (contents
  are moved to struct acpi_pci_root). This simplify the code, and we
  no longer care about kmalloc() failure.

- We can make pci_acpi_osc_support() be a static function, which is
  called only from drivers/acpi/pci_root.c.

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Reviewed-by: Andrew Patterson <andrew.patterson@hp.com>
Tested-by: Andrew Patterson <andrew.patterson@hp.com>
Acked-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>