input: sensors: create dedicate workqueue for sensors

Default system workqueue may be bounded on specific cpu, that cpu
will always be wakeup to handle the workqueue, this will consume
extra power in some case. This change fix issue by create dedicate
sensor workqueue which not bounded to any cpu.

Change-Id: I38f64def943625cc525b56e863a4ef5384bc10ac
Signed-off-by: Bingzhe Cai <bingzhec@codeaurora.org>