cpufreq: powernow-k8: Suppress checkpatch warnings

Suppress the following checkpatch.pl warnings:

 - WARNING: Prefer pr_err(... to printk(KERN_ERR ...
 - WARNING: Prefer pr_info(... to printk(KERN_INFO ...
 - WARNING: Prefer pr_warn(... to printk(KERN_WARNING ...
 - WARNING: quoted string split across lines
 - WARNING: please, no spaces at the start of a line

Also, define the pr_fmt macro instead of PFX for the module name.

Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>