[PATCH] macintosh: don't store i2c_add_driver() return if no further processing done

therm_pm72.c and windfarm_lm75_sensor.c both store the return from
i2c_add_driver() but do no further processing on the result.  Simply return
what i2c_add_driver() did, instead.

Signed-off-by: Arthur Othieno <a.othieno@bluewin.ch>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>