powerpc: T104XRDB: Split to T1040RDB and T1042RDB in Kconfig

Split ARCH_T104XRDB as ARCH_T1040RDB and ARCH_T1042RDB in Kconfig to
simplify config options.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/configs/T1040RDB_SPIFLASH_defconfig b/configs/T1040RDB_SPIFLASH_defconfig
index 31ea589..3158821 100644
--- a/configs/T1040RDB_SPIFLASH_defconfig
+++ b/configs/T1040RDB_SPIFLASH_defconfig
@@ -8,7 +8,7 @@
 CONFIG_SPL_SPI_FLASH_SUPPORT=y
 CONFIG_SPL_SPI_SUPPORT=y
 CONFIG_MPC85xx=y
-CONFIG_TARGET_T104XRDB=y
+CONFIG_TARGET_T1040RDB=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y