kconfig: remove redundant "SPL" from CONFIG_SYS_EXTRA_OPTIONS

CONFIG_SPL is defined as a primary option in Kconfig.
It should not be added to CONFIG_SYS_EXTRA_OPTIONS.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
diff --git a/configs/Mini-X_defconfig b/configs/Mini-X_defconfig
index ea0c786..6229fb8 100644
--- a/configs/Mini-X_defconfig
+++ b/configs/Mini-X_defconfig
@@ -1,5 +1,5 @@
 CONFIG_SPL=y
-CONFIG_SYS_EXTRA_OPTIONS="MINI_X,SPL,AXP209_POWER,USB_EHCI"
+CONFIG_SYS_EXTRA_OPTIONS="MINI_X,AXP209_POWER,USB_EHCI"
 CONFIG_FTDFILE="sun4i-a10-mini-xplus.dtb"
 +S:CONFIG_ARM=y
 +S:CONFIG_TARGET_SUN4I=y