soc: mediatek: cmdq: Don't log an error when gce-client-reg is not found

Most of the callers to this function do not require CMDQ support, it is
optional, so the missing property shouldn't cause an error message.
However, it could result on degraded performance, so the fact that it's
missing should still be alerted. Furthermore, the callers that do
require CMDQ support already log at the error level when an error is
returned.

Change the log message in this helper to be printed at the warning level
instead.

Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20240229-gce-client-reg-log-dbg-v2-1-4975077173d0@collabora.com


Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>