hwmon: (coretemp) Don't use threshold registers for tempX_max

With commit c814a4c7, the meaning of tempX_max
was changed. It no longer returns the value of bits 8:15 of
MSR_IA32_TEMPERATURE_TARGET, but instead returns the value of CPU threshold
register T1. tempX_max_hyst was added to reflect the value of temperature
threshold register T0.

As it turns out, T0 and T1 are used on some systems, presumably by the BIOS.
Also, T0 and T1 don't have a well defined meaning. The thresholds may be used
as upper or lower limits, and it is not guaranteed that T0 <= T1. Thus, the new
attribute mapping does not reflect the actual usage of the threshold registers.
Also, register contents are changed during runtime by an entity other than the
hwmon driver, meaning the values cached by the driver do not reflect actual
register contents.

Revert most of c814a4c7 to address the problem.
Support for T0 and T1 will be added back in with a separate commit, using new
attribute names.

Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Durgadoss R <durgadoss.r@intel.com>
Acked-by: Jean Delvare <khali@linux-fr.org>