powerpc: T1042: Remove macro CONFIG_PPC_T1042

Replace CONFIG_PPC_T1042 with ARCH_T1024 in Kconfig and clean up
existing macros.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/configs/T1042RDB_PI_SPIFLASH_defconfig b/configs/T1042RDB_PI_SPIFLASH_defconfig
index 433f933..483980b 100644
--- a/configs/T1042RDB_PI_SPIFLASH_defconfig
+++ b/configs/T1042RDB_PI_SPIFLASH_defconfig
@@ -14,7 +14,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="PPC_T1042,T1042RDB_PI,RAMBOOT_PBL,SPL_FSL_PBL,SPIFLASH"
+CONFIG_SYS_EXTRA_OPTIONS="T1042RDB_PI,RAMBOOT_PBL,SPL_FSL_PBL,SPIFLASH"
 CONFIG_BOOTDELAY=10
 CONFIG_SILENT_CONSOLE=y
 # CONFIG_CONSOLE_MUX is not set