hwmon: (lm85) Fix function RANGE_TO_REG()

Function RANGE_TO_REG() is broken. For a requested range of 2000 (2
degrees C), it will return an index value of 15, i.e. 80.0 degrees C,
instead of the expected index value of 0. All other values are handled
properly, just 2000 isn't.

The bug was introduced back in November 2004 by this patch:
http://git.kernel.org/?p=linux/kernel/git/tglx/history.git;a=commit;h=1c28d80f1992240373099d863e4996cdd5d646d0



While this can be fixed easily with the current code, I'd rather
rewrite the whole function in a way which is more obviously correct.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Justin Thiessen <jthiessen@penguincomputing.com>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>