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/zynq_zc770_xm012_defconfig b/configs/zynq_zc770_xm012_defconfig
index 0401739..341a4d8 100644
--- a/configs/zynq_zc770_xm012_defconfig
+++ b/configs/zynq_zc770_xm012_defconfig
@@ -1,8 +1,8 @@
 CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS="ZC770_XM012"
-+S:CONFIG_ARM=y
-+S:CONFIG_ZYNQ=y
-+S:CONFIG_TARGET_ZYNQ_ZC770=y
+CONFIG_ARM=y
+CONFIG_ZYNQ=y
+CONFIG_TARGET_ZYNQ_ZC770=y
 CONFIG_OF_CONTROL=y
 CONFIG_DEFAULT_DEVICE_TREE="zynq-zc770-xm012"
 CONFIG_FIT=y