firmware: qcom: scm: fix bogus irq error at probe

A recent commit added support for an optional interrupt which is only
available on some platforms.

Stop spamming the logs with bogus error messages on platforms that do
not use this new optional resource:

	qcom_scm firmware:scm: error -ENXIO: IRQ index 0 not found

Fixes: 6bf32599 ("firmware: qcom: scm: Add wait-queue handling logic")
Cc: Guru Das Srinagesh <quic_gurus@quicinc.com>
Cc: Sibi Sankar <quic_sibis@quicinc.com>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Tested-by: Steev Klimaszewski <steev@kali.org> # Thinkpad X13s
Acked-by: Guru Das Srinagesh <quic_gurus@quicinc.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230309111209.31606-1-johan+linaro@kernel.org

drivers/firmware/qcom_scm.c

@@ -1479,7 +1479,7 @@ static int qcom_scm_probe(struct platform_device *pdev)
 
 	init_completion(&__scm->waitq_comp);
 
-	irq = platform_get_irq(pdev, 0);
+	irq = platform_get_irq_optional(pdev, 0);
 	if (irq < 0) {
 		if (irq != -ENXIO)
 			return irq;