mfd/da9052: make i2c_device_id array const

This is possible since *of_device_id.data became const. While at it also
drop a cast to const that was never needed.

[ukl: split Arnd's patch by driver and add changlog]

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>