The lm87 driver normally assumes that firmware configured the chip
correctly.  Since this is not always the case, alllow platform code to
set the channel register value via platform_data.  All other
configuration registers can be changed after driver initialisation.
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: NJean Delvare <khali@linux-fr.org>