hwmon: (lm85) Export in5, in6 and in7 voltage channels

The SMSC EMC6D100 supports 3 additional voltage channels. The lm85
driver reads the register values for these, but doesn't create the
corresponding sysfs files, so the user can't read the values nor write
the limits. Create the missing sysfs files.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Juerg Haefliger <juergh at gmail.com>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>