platform/x86: thinkpad_acpi: Add labels to the first 2 temperature sensors

On EC version 3, the first 2 temperature sensors are always CPU and GPU
add labels for these.

This changes e.g. the "sensors" command output on a X1C8 from:

thinkpad-isa-0000
Adapter: ISA adapter
fan1:        2694 RPM
temp1:        +42.0°C
temp2:            N/A
temp3:        +33.0°C
temp4:         +0.0°C
temp5:        +35.0°C
temp6:        +42.0°C
temp7:        +42.0°C
temp8:            N/A

into:

thinkpad-isa-0000
Adapter: ISA adapter
fan1:        2694 RPM
CPU:          +42.0°C
GPU:              N/A
temp3:        +33.0°C
temp4:         +0.0°C
temp5:        +35.0°C
temp6:        +42.0°C
temp7:        +42.0°C
temp8:            N/A

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210413072112.183550-1-hdegoede@redhat.com