firmware: qcom_scm: Add missing is_available API

Add back function that was dropped when reworking the SCM code.
Signed-off-by: Andy Gross <andy.gross@linaro.org>

drivers/firmware/qcom_scm.c

@@ -308,6 +308,14 @@ static const struct reset_control_ops qcom_scm_pas_reset_ops = {
 	.deassert = qcom_scm_pas_reset_deassert,
 };
 
+/**
+ * qcom_scm_is_available() - Checks if SCM is available
+ */
+bool qcom_scm_is_available(void)
+{
+	return !!__scm;
+}
+EXPORT_SYMBOL(qcom_scm_is_available);
 
 static int qcom_scm_probe(struct platform_device *pdev)
 {