powerpc: T1040D4RDB: Separate from T1040RDB in Kconfig

Use TARGET_T1040D4RDB in Kconfig to simplify config macros. Replace
CONFIG_T1040D4RDB with TARGET_T1040D4RDB and clean up existing macros.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/configs/T1040D4RDB_SDCARD_defconfig b/configs/T1040D4RDB_SDCARD_defconfig
index 35a261f..4b9faab 100644
--- a/configs/T1040D4RDB_SDCARD_defconfig
+++ b/configs/T1040D4RDB_SDCARD_defconfig
@@ -7,12 +7,12 @@
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_DRIVERS_MISC_SUPPORT=y
 CONFIG_MPC85xx=y
-CONFIG_TARGET_T1040RDB=y
+CONFIG_TARGET_T1040D4RDB=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="T1040D4RDB,RAMBOOT_PBL,SPL_FSL_PBL,SDCARD,T104XD4RDB,SYS_FSL_DDR4"
+CONFIG_SYS_EXTRA_OPTIONS="RAMBOOT_PBL,SPL_FSL_PBL,SDCARD,T104XD4RDB,SYS_FSL_DDR4"
 CONFIG_BOOTDELAY=10
 CONFIG_SILENT_CONSOLE=y
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y