feat(imx8m): add the ddr frequency change support for imx8m family

Add the DDR frequency change support.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Change-Id: If1167785796b8678c351569b83d2922c66f6e530
diff --git a/plat/imx/common/imx_sip_svc.c b/plat/imx/common/imx_sip_svc.c
index fd54820..21f7ec7 100644
--- a/plat/imx/common/imx_sip_svc.c
+++ b/plat/imx/common/imx_sip_svc.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2022, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -34,6 +34,10 @@
 		SMC_RET1(handle, imx_soc_info_handler(smc_fid, x1, x2, x3));
 		break;
 #endif
+#if defined(PLAT_imx8mm) || defined(PLAT_imx8mn) || defined(PLAT_imx8mp)
+	case IMX_SIP_DDR_DVFS:
+		return dram_dvfs_handler(smc_fid, handle, x1, x2, x3);
+#endif
 #if (defined(PLAT_imx8qm) || defined(PLAT_imx8qx))
 	case  IMX_SIP_SRTC:
 		return imx_srtc_handler(smc_fid, handle, x1, x2, x3, x4);