acpi_get_devices() returns success if it did not find any device.
We have to check for this case.
Signed-off-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Tested-by: Daniel Ritz <daniel.ritz-ml@swissonline.ch>
Tested-by: Luca <kronos.it@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>