refactor(tc): append binding for SMMU-700

The usage for SMMU-700 is not consistent across TC platforms:

  SMMU-700 on TC2:

          | FVP   | FPGA
  --------+-------+------
  Display | Used  | Used
  GPU     | Used  | Used

  SMMU-700 on TC3:

          | FVP   | FPGA
  --------+-------+------
  Display | No    | No
  GPU     | Used  | No

This commit changes to use append mode for SMMU-700 to bind it on TC2
and TC3 separately. As a result, the TC_IOMMU_EN configuration is not
used, remove it.

Change-Id: Ic4152eb4c8ef97bf27b8a97c3c6cb86e32a2e8eb
Signed-off-by: Leo Yan <leo.yan@arm.com>
diff --git a/fdts/tc2.dts b/fdts/tc2.dts
index 69c6886..4946aca 100644
--- a/fdts/tc2.dts
+++ b/fdts/tc2.dts
@@ -237,9 +237,18 @@
 		};
 	};
 
+	smmu_700: iommu@3f000000 {
+		status = "okay";
+	};
+
 	dp0: display@DPU_ADDR {
 #if TC_SCMI_PD_CTRL_EN
 		power-domains = <&scmi_devpd (PLAT_MAX_CPUS_PER_CLUSTER + 2)>;
 #endif
+		iommus = <&smmu_700 0x100>;
+	};
+
+	gpu: gpu@2d000000 {
+		iommus = <&smmu_700 0x200>;
 	};
 };