Add kerneldoc comments to acpi_os_map_iomem() and acpi_os_unmap_iomem()
and explain why the latter needs the __ref annotation in one of them
(as suggested by Mathias Krause).
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: NMathias Krause <minipli@googlemail.com>