kconfig: remove meaningless prefixes in defconfig files

Since commit e02ee2548afe (kconfig: switch to single .config
configuration), the prefixes in defconfig files such as "+S:",
"+ST:", etc., are meaningless.

This commit was generated by the following command:

  find configs -name '*_defconfig' | xargs sed -i 's/^+*S*T*://'

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/configs/snow_defconfig b/configs/snow_defconfig
index 353ddb0..2b0d6fa 100644
--- a/configs/snow_defconfig
+++ b/configs/snow_defconfig
@@ -1,7 +1,7 @@
 CONFIG_SPL=y
-+S:CONFIG_ARM=y
-+S:CONFIG_ARCH_EXYNOS=y
-+S:CONFIG_TARGET_SNOW=y
+CONFIG_ARM=y
+CONFIG_ARCH_EXYNOS=y
+CONFIG_TARGET_SNOW=y
 CONFIG_DEFAULT_DEVICE_TREE="exynos5250-snow"
 CONFIG_CROS_EC=y
 CONFIG_DM_CROS_EC=y