ACPI/PCI: handle multiple _OSC

ACPI/PCI: handle multiple _OSC

The pci_osc_control_set() function can be called for the ACPI object
that doesn't have _OSC method. In this case, acpi_get_osc_data() would
allocate a useless memory region. To avoid this, we need to check the
existence of _OSC before calling acpi_get_osc_data(). Here is a patch
to fix this problem in pci_osc_control_set.

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>