firmware: qcom: scm: suppress download mode error

Stop spamming the logs with errors about missing mechanism for setting
the so called download (or dump) mode for users that have not requested
that feature to be enabled in the first place.

This avoids the follow error being logged on boot as well as on
shutdown when the feature it not available and download mode has not
been enabled on the kernel command line:

	qcom_scm firmware:scm: No available mechanism for setting download mode

Fixes: 79cb2cb ("firmware: qcom: scm: Disable SDI and write no dump to dump mode")
Fixes: 781d32d ("firmware: qcom_scm: Clear download bit during reboot")
Cc: Mukesh Ojha <quic_mojha@quicinc.com>
Cc: stable@vger.kernel.org	# 6.4
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
Link: https://lore.kernel.org/r/20241002100122.18809-2-johan+linaro@kernel.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

drivers/firmware/qcom/qcom_scm.c

@@ -545,7 +545,7 @@ static void qcom_scm_set_download_mode(u32 dload_mode)
 	} else if (__qcom_scm_is_call_available(__scm->dev, QCOM_SCM_SVC_BOOT,
 						QCOM_SCM_BOOT_SET_DLOAD_MODE)) {
 		ret = __qcom_scm_set_dload_mode(__scm->dev, !!dload_mode);
-	} else {
+	} else if (dload_mode) {
 		dev_err(__scm->dev,
 			"No available mechanism for setting download mode\n");
 	}