staging/ste_rmi4: 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 This is obsolete meanwhile, the core will do it.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: Naveen Kumar Gaddipati <naveen.gaddipati@stericsson.com>
Cc: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>