powerpc: T1042D4RDB: Separate from T1042RDB in Kconfig

Use TARGET_T1042D4RDB in Kconfig to simplify config options.
Remove macro CONFIG_T1042D4RDB.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/board/freescale/t104xrdb/Kconfig b/board/freescale/t104xrdb/Kconfig
index 410c9a5..e33d317 100644
--- a/board/freescale/t104xrdb/Kconfig
+++ b/board/freescale/t104xrdb/Kconfig
@@ -1,4 +1,6 @@
-if TARGET_T1040RDB || TARGET_T1040D4RDB || TARGET_T1042RDB || TARGET_T1042RDB_PI
+if TARGET_T1040RDB || TARGET_T1040D4RDB || \
+	TARGET_T1042RDB || TARGET_T1042D4RDB || \
+	TARGET_T1042RDB_PI
 
 config SYS_BOARD
 	default "t104xrdb"
diff --git a/board/freescale/t104xrdb/eth.c b/board/freescale/t104xrdb/eth.c
index cbce840..9d8ead4 100644
--- a/board/freescale/t104xrdb/eth.c
+++ b/board/freescale/t104xrdb/eth.c
@@ -62,7 +62,7 @@
 						CONFIG_SYS_SGMII1_PHY_ADDR);
 			break;
 #endif
-#ifdef CONFIG_T1042D4RDB
+#ifdef CONFIG_TARGET_T1042D4RDB
 		case PHY_INTERFACE_MODE_SGMII:
 			/* T1042D4RDB supports SGMII on DTSEC1, DTSEC2
 			 *  & DTSEC3