feat(imx8m): add the PU power domain support on imx8mm/mn

Add the PU power domain support for imx8mm/mn.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Change-Id: Ib88b4b5db956fdf2c77d2f2f3723d61a7060409d
diff --git a/plat/imx/common/imx_sip_svc.c b/plat/imx/common/imx_sip_svc.c
index 21f7ec7..fae9750 100644
--- a/plat/imx/common/imx_sip_svc.c
+++ b/plat/imx/common/imx_sip_svc.c
@@ -37,6 +37,9 @@
 #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);
+	case IMX_SIP_GPC:
+		SMC_RET1(handle, imx_gpc_handler(smc_fid, x1, x2, x3));
+		break;
 #endif
 #if (defined(PLAT_imx8qm) || defined(PLAT_imx8qx))
 	case  IMX_SIP_SRTC: