imx: add imx8qm/imx8qx SRTC SIP runtime service support

On i.MX8QM/i.MX8QX with system controller inside, the SRTC is
managed by SCFW(system controller firmware) and some functions
like setting SRTC's time etc. can ONLY be requested from secure
world, so SIP runtime service is needed for such kind of operations,
this patch adds SRTC SIP runtime service support for i.MX8QM and
i.MX8QX.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
diff --git a/plat/imx/common/imx_sip_handler.c b/plat/imx/common/imx_sip_handler.c
new file mode 100644
index 0000000..a414a44
--- /dev/null
+++ b/plat/imx/common/imx_sip_handler.c
@@ -0,0 +1,44 @@
+/*
+ * Copyright 2019 NXP
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <std_svc.h>
+#include <platform_def.h>
+#include <common/debug.h>
+#include <common/runtime_svc.h>
+#include <imx_sip_svc.h>
+#include <sci/sci.h>
+
+static int imx_srtc_set_time(uint32_t year_mon,
+			unsigned long day_hour,
+			unsigned long min_sec)
+{
+	return sc_timer_set_rtc_time(ipc_handle,
+		year_mon >> 16, year_mon & 0xffff,
+		day_hour >> 16, day_hour & 0xffff,
+		min_sec >> 16, min_sec & 0xffff);
+}
+
+int imx_srtc_handler(uint32_t smc_fid,
+		    void *handle,
+		    u_register_t x1,
+		    u_register_t x2,
+		    u_register_t x3,
+		    u_register_t x4)
+{
+	int ret;
+
+	switch (x1) {
+	case IMX_SIP_SRTC_SET_TIME:
+		ret = imx_srtc_set_time(x2, x3, x4);
+		break;
+	default:
+		ret = SMC_UNK;
+	}
+
+	SMC_RET1(handle, ret);
+}