powerpc: T4240: Remove macro CONFIG_PPC_T4240

Use CONFIG_ARCH_T4240 from Kconfig instead.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/configs/T4240QDS_SDCARD_defconfig b/configs/T4240QDS_SDCARD_defconfig
index 8f8837c..2357d82 100644
--- a/configs/T4240QDS_SDCARD_defconfig
+++ b/configs/T4240QDS_SDCARD_defconfig
@@ -12,7 +12,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="PPC_T4240,RAMBOOT_PBL,SPL_FSL_PBL,SDCARD"
+CONFIG_SYS_EXTRA_OPTIONS="RAMBOOT_PBL,SPL_FSL_PBL,SDCARD"
 CONFIG_BOOTDELAY=10
 CONFIG_SPL=y
 CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT=y