powerpc: T1042RDB_PI: Split from T1042RDB in Kconfig

Use separated TARGET_T1042RDB_PI to simplify config options.
Remove macro CONFIG_T1042RDB_PI.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/configs/T1042RDB_PI_NAND_defconfig b/configs/T1042RDB_PI_NAND_defconfig
index e15c3c4..d8aa1f7 100644
--- a/configs/T1042RDB_PI_NAND_defconfig
+++ b/configs/T1042RDB_PI_NAND_defconfig
@@ -8,12 +8,12 @@
 CONFIG_SPL_DRIVERS_MISC_SUPPORT=y
 CONFIG_VIDEO=y
 CONFIG_MPC85xx=y
-CONFIG_TARGET_T1042RDB=y
+CONFIG_TARGET_T1042RDB_PI=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="T1042RDB_PI,RAMBOOT_PBL,SPL_FSL_PBL,NAND"
+CONFIG_SYS_EXTRA_OPTIONS="RAMBOOT_PBL,SPL_FSL_PBL,NAND"
 CONFIG_BOOTDELAY=10
 CONFIG_SILENT_CONSOLE=y
 # CONFIG_CONSOLE_MUX is not set