max17042_battery: Remove obsolete cleanup for clientdata

A few new i2c-drivers came into the kernel which clear the
clientdata-pointer on exit or error. This is obsolete meanwhile,
the core will do it.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>