HID: i2c-hid: set power sleep before shutdown

Add i2c_hid_shutdown for i2c-hid driver to send suspend cmd & free
irq before device shutdown.

Some HW design (i.e. Umaro, a chromebook model) is that the power to
i2c hid device won't down after device shutdown. Also the i2c-hid driver
do not send suspend cmd to the hid i2c device and free its irq before
shutdown.So if We touch the touchscreen or some other i2c hid device,
the power consumtion will be go up even when the device is in shutdown
state.

Though the root cause maybe a HW issue. But it seems that it is a
good pratice to set power sleep for i2c-hid device before shutdown.

Signed-off-by: Guohua Zhong <ghzhong@yifangdigital.com>
Acked-By: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>