rtc: Drop explicit initialization of struct i2c_device_id::driver_data to 0

rtc: Drop explicit initialization of struct i2c_device_id::driver_data to 0

These drivers don't use the driver_data member of struct i2c_device_id,
so don't explicitly initialize this member.

This prepares putting driver_data in an anonymous union which requires
either no initialization or named designators. But it's also a nice
cleanup on its own.

While add it, also remove a comma after the sentinel entry in
rtc-hym8563.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20240515194336.58342-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>