w1/slaves: use pr_* instead of printk

This patch replaces all calls to the "printk" function within the "slaves"
subdirectory by calls to the appropriate "pr_*" function thus addressing
the following warning generated by the checkpatch script:

WARNING: Prefer [subsystem eg: netdev]_err([subsystem]dev, ...
        then dev_err(dev, ... then pr_err(...  to printk(KERN_ERR ...

Signed-off-by: Fjodor Schelichow <fjodor.schelichow@hotmail.com>
Signed-off-by: Roman Sommer <romsom2@yahoo.de>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>