[PATCH] I2C: update max6875 documentation

Updates to the max6875 driver documentation.
This brings the documentation in sync with the code, which was recently
simplified.

This patch is based off 2.6.13-rc2-mm2.

Signed-off-by: Ben Gardner <bgardner@wabtec.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>