ACPI: Document handle_eject_request() arguments

Add argument descriptions to the handle_eject_request() kerneldoc
comment.

Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>