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/board/freescale/t208xqds/Kconfig b/board/freescale/t208xqds/Kconfig
index 4e329dd..26ef530 100644
--- a/board/freescale/t208xqds/Kconfig
+++ b/board/freescale/t208xqds/Kconfig
@@ -1,4 +1,4 @@
-if TARGET_T208XQDS
+if TARGET_T2080QDS || TARGET_T2081QDS
 
 config SYS_BOARD
 	default "t208xqds"