soc: qcom: rmtfs: handle optional qcom,vmid correctly

Older platforms don't have qcom,vmid set, handle -EINVAL return value
correctly. And since num_vmids is passed to of_property_read_u32_array
later we should make sure it has a sane value before continuing.

Fixes: e656cd0bcf ("soc: qcom: rmtfs: Optionally map RMTFS to more VMs")
Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230305-rmtfs-vmid-fix-v1-2-6a7206081602@z3ntu.xyz

drivers/soc/qcom/rmtfs_mem.c

@@ -229,7 +229,10 @@ static int qcom_rmtfs_mem_probe(struct platform_device *pdev)
 	}
 
 	num_vmids = of_property_count_u32_elems(node, "qcom,vmid");
-	if (num_vmids < 0) {
+	if (num_vmids == -EINVAL) {
+		/* qcom,vmid is optional */
+		num_vmids = 0;
+	} else if (num_vmids < 0) {
 		dev_err(&pdev->dev, "failed to count qcom,vmid elements: %d\n", num_vmids);
 		goto remove_cdev;
 	} else if (num_vmids > NUM_MAX_VMIDS) {