thermal: Do not log an error if thermal_zone_get_temp returns -EAGAIN

Some temperature sensors only get updated every few seconds and while
waiting for the first irq reporting a (new) temperature to happen there
get_temp operand will return -EAGAIN as it does not have any data to report
yet.

Not logging an error in this case avoids messages like these from showing
up in dmesg on affected systems:

[    1.219353] thermal thermal_zone0: failed to read out thermal zone 0
[    2.015433] thermal thermal_zone0: failed to read out thermal zone 0
[    2.416737] thermal thermal_zone0: failed to read out thermal zone 0

Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>