ACPI: Fix CONFIG_ACPI_DOCK=n compiler warning

Recently the ACPI ops structs were constified but the inline version
of register_hotplug_dock_device() was overlooked (see also commit
9c8b04be, June 25 2011). Update the inline function
register_hotplug_dock_device() that is enabled with
CONFIG_ACPI_DOCK=n too. This patch fixes at least the following
compiler warnings:

drivers/ata/libata-acpi.c: In function .ata_acpi_associate.:
drivers/ata/libata-acpi.c:266:11: warning: passing argument 2 of .register_hotplug_dock_device. discards qualifiers from pointer target type
include/acpi/acpi_drivers.h:146:19: note: expected .struct acpi_dock_ops *. but argument is of type .const struct acpi_dock_ops *.
drivers/ata/libata-acpi.c:275:11: warning: passing argument 2 of .register_hotplug_dock_device. discards qualifiers from pointer target type
include/acpi/acpi_drivers.h:146:19: note: expected .struct acpi_dock_ops *. but argument is of type .const struct acpi_dock_ops *.

Cc: stable@vger.kernel.org
Signed-off-by: Len Brown <len.brown@intel.com>

include/acpi/acpi_drivers.h

@@ -144,7 +144,7 @@ static inline void unregister_dock_notifier(struct notifier_block *nb)
 {
 }
 static inline int register_hotplug_dock_device(acpi_handle handle,
-					       struct acpi_dock_ops *ops,
+					       const struct acpi_dock_ops *ops,
 					       void *context)
 {
 	return -ENODEV;