ACPI: bus: Introduce wrappers for ACPICA notify handler install/remove

Introduce new functions acpi_dev_install_notify_handler() and
acpi_dev_remove_notify_handler(), to install and remove, respectively,
a handler for AML Notify() operations targeted at a given ACPI device
object. They will allow drivers to install Notify() handlers directly
instead of providing an ACPI driver .notify() callback to be invoked
in the context of a Notify() handler installed by the ACPI bus type
code. In particular, this will help platform drivers to provide
Notify() handlers for the ACPI companions of the platform devices
they bind to.

These functions are replacements for acpi_device_install_notify_handler()
and acpi_device_remove_notify_handler(), respectively, and after all
drivers switch over to using them, the old ones will be dropped.

Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Michal Wilczynski <michal.wilczynski@intel.com>
[ rjw: Subject and changelog edits, whitespace adjustments ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>