Rearrange the tjmax handling code so that it can be used directly in
the sysfs attribute callbacks without forward declarations.

No functional change in this patch.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Link: https://lore.kernel.org/r/20221113153145.32696-2-rui.zhang@intel.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>