We have pr_fmt() in sysfs.c but we still use pr_err(PREFIX ...) which
is wrong, remove the duplicated PREFIX and also using pr_* to replace
printk to simlify the code.
Signed-off-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>