hwmon: (coretemp) rearrange tjmax handing code

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.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>