Fix the compiler error when the CONFIG_PM_OPS flag is not set.

drivers/iio/light/tsl4531.c:235:8: error: ‘tsl4531_suspend’ undeclared here (not in a function)
drivers/iio/light/tsl4531.c:235:8: error: ‘tsl4531_resume’ undeclared here (not in a function)
Signed-off-by: NDan Murphy <dmurphy@ti.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

driver for the TSL4531 family of 16-bit I2C ambient light
sensors; information is here:
http://www.ams.com/eng/Products/Light-Sensors/Ambient-Light-Sensor-ALS/TSL45315

the chip offers simple lux output

v3 (thanks Lars-Peter Clausen):
* add mutex to when updating integration time
* fix chip ID checking
* code cleanups
v2:
* rename to tsl4351
* use INT_TIME
Signed-off-by: NPeter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>