HID: hid-steam: Add Deck IMU support

The Deck's controller features an accelerometer and gyroscope which
send their measurement values by default in the main HID input report.
Expose both sensors to userspace through a separate evdev node as it
is done by the hid-nintendo and hid-playstation drivers.

Signed-off-by: Max Maisel <mmm-1@posteo.net>
Reviewed-by: Vicki Pfau <vi@endrift.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>