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_SPIFLASH_defconfig b/configs/BSC9131RDB_SPIFLASH_defconfig
index 47b4486..2c5d637 100644
--- a/configs/BSC9131RDB_SPIFLASH_defconfig
+++ b/configs/BSC9131RDB_SPIFLASH_defconfig
@@ -5,7 +5,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="BSC9131RDB,SPIFLASH"
+CONFIG_SYS_EXTRA_OPTIONS="SPIFLASH"
 CONFIG_BOOTDELAY=10
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_HUSH_PARSER=y