Define pr_fmt macro to add a prefix to the message,
this can make the thermal log better recognized.

Before:

[    0.602672] nfc: nfc_init: NFC Core ver 0.1
[    0.602828] NET: Registered protocol family 39
[    0.603435] clocksource: Switched to clocksource mct-frc
[    0.746216] failed to build thermal zone cpu-thermal: -22
[    0.746451] NET: Registered protocol family 2

After:

[    0.602804] NET: Registered protocol family 39
[    0.603463] clocksource: Switched to clocksource mct-frc
[    0.746309] thermal_sys: failed to build thermal zone cpu-thermal: -22
[    0.746545] NET: Registered protocol family 2

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>