powerpc: BSC9131RDB: Remove CONFIG_BSC9131RDB macro

This macro CONFIG_BSC9131RDB is no longer needed.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/configs/BSC9131RDB_NAND_defconfig b/configs/BSC9131RDB_NAND_defconfig
index ad24afa..5c4d45d 100644
--- a/configs/BSC9131RDB_NAND_defconfig
+++ b/configs/BSC9131RDB_NAND_defconfig
@@ -7,7 +7,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="BSC9131RDB,NAND"
+CONFIG_SYS_EXTRA_OPTIONS="NAND"
 CONFIG_BOOTDELAY=10
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_SPL=y