powerpc: T208XQDS: Split as T2080QDS and T2081QDS

Use two separated targets in Kconfig to simplify configurations.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/configs/T2081QDS_NAND_defconfig b/configs/T2081QDS_NAND_defconfig
index 410d375..b16ef2b 100644
--- a/configs/T2081QDS_NAND_defconfig
+++ b/configs/T2081QDS_NAND_defconfig
@@ -7,7 +7,7 @@
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_DRIVERS_MISC_SUPPORT=y
 CONFIG_MPC85xx=y
-CONFIG_TARGET_T208XQDS=y
+CONFIG_TARGET_T2081QDS=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y