Removed unused references to CONFIG_SERIALx

After creating CONS_INDEX and migrating a bunch of boards to it,
there are a bunch of defined references to CONFIG_SERIALx which
are not referenced in any C code or #ifdef, so they can now be
removed

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/configs/brxre1_defconfig b/configs/brxre1_defconfig
index 14a49db..c56a633 100644
--- a/configs/brxre1_defconfig
+++ b/configs/brxre1_defconfig
@@ -9,7 +9,7 @@
 CONFIG_SPL_SERIAL_SUPPORT=y
 CONFIG_SPL=y
 CONFIG_NR_DRAM_BANKS=1
-CONFIG_SYS_EXTRA_OPTIONS="SERIAL1,CONS_INDEX=1"
+CONFIG_SYS_EXTRA_OPTIONS="CONS_INDEX=1"
 CONFIG_BOOTDELAY=-2
 # CONFIG_CONSOLE_MUX is not set
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y