powerpc: T1023: Remove macro CONFIG_PPC_T1023

Replace CONFIG_PPC_T1023 with ARCH_T1023 in Kconfig and clean up
existing macros.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/configs/T1023RDB_defconfig b/configs/T1023RDB_defconfig
index 1c3510a..ef0005e 100644
--- a/configs/T1023RDB_defconfig
+++ b/configs/T1023RDB_defconfig
@@ -5,7 +5,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="PPC_T1023,T1023RDB"
+CONFIG_SYS_EXTRA_OPTIONS="T1023RDB"
 CONFIG_BOOTDELAY=10
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_HUSH_PARSER=y