drivers: thermal: processor_thermal: Downgrade error message

drivers: thermal: processor_thermal: Downgrade error message

BugLink: https://bugs.launchpad.net/bugs/1824690
Downgrade "Unsupported event" message from dev_err to dev_dbg. Otherwise it
floods with this message one some platforms.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
(backported from commit 44c0c23725a16c8803b8809b87651405e8741e4d)
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: You-Sheng Yang <vicamo.yang@canonical.com>
Acked-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>