carl9170: devres-ing input_allocate_device

devres will take care of freeing the input_device once
it is no longer needed.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/f81a6ff3b02116c6a448c42eecb546ea5d46c108.1646250537.git.chunkeey@gmail.com