hwmon: (lm78) Use pr_fmt and pr_<level>

Added #define pr_fmt KBUILD_MODNAME ": " fmt
Converted printks to pr_<level>
Coalesced any long formats
Removed prefixes from formats

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>