Because acpi_bus_get_acpi_device() is completely analogous to
acpi_fetch_acpi_dev(), rename it to acpi_get_acpi_dev() and
add a kerneldoc comment to it.

Accordingly, rename acpi_bus_put_acpi_device() to acpi_put_acpi_dev()
and update all of the users of these two functions.

While at it, move the acpi_fetch_acpi_dev() header next to the
acpi_get_acpi_dev() header in the header file holding them.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Punit Agrawal <punit.agrawal@bytedance.com>