powerpc: T2080RDB: Rename from T208XRDB in Kconfig

T208XRDB only has one target T2080RDB. Use TARGET_T2080RDB in Kconfig
and clean up existing macros.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/arch/powerpc/cpu/mpc85xx/Kconfig b/arch/powerpc/cpu/mpc85xx/Kconfig
index abd7349..e4a7b88 100644
--- a/arch/powerpc/cpu/mpc85xx/Kconfig
+++ b/arch/powerpc/cpu/mpc85xx/Kconfig
@@ -247,8 +247,8 @@
 	select SUPPORT_SPL
 	select PHYS_64BIT
 
-config TARGET_T208XRDB
-	bool "Support T208xRDB"
+config TARGET_T2080RDB
+	bool "Support T2080RDB"
 	select SUPPORT_SPL
 	select PHYS_64BIT