thermal_sys: convert printks to pr_<level>

Use the current logging style.

Remove PREFIX, add pr_fmt, convert the printks.  All dmesg output now
prefixed with "thermal_sys: ".

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Jesper Juhl <jj@chaosbits.net>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>