powerpc: T1040RDB: Remove macro CONFIG_T1040RDB

Use CONFIG_TARGET_T1040RDB instead.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/configs/T1040RDB_NAND_defconfig b/configs/T1040RDB_NAND_defconfig
index a50eab9..2129bf4 100644
--- a/configs/T1040RDB_NAND_defconfig
+++ b/configs/T1040RDB_NAND_defconfig
@@ -12,7 +12,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="T1040RDB,RAMBOOT_PBL,SPL_FSL_PBL,NAND"
+CONFIG_SYS_EXTRA_OPTIONS="RAMBOOT_PBL,SPL_FSL_PBL,NAND"
 CONFIG_BOOTDELAY=10
 CONFIG_SILENT_CONSOLE=y
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y