input: sensors: change sensors classdev device's parent to input devices

Sensor HAL takes long time to scan /dev/input to get information
from input subsystem. Change sensors sysfs hierarchy to avoid
the scanning to reduce sensor HAL initialization time.

Change-Id: Ifcd560dacdba2600f2ae5d40a5c3e639ea291274
Signed-off-by: Sudhakar Manapati <smanap@codeaurora.org>