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/P1010RDB-PB_NAND_defconfig b/configs/P1010RDB-PB_NAND_defconfig
index 0125164..1e11593 100644
--- a/configs/P1010RDB-PB_NAND_defconfig
+++ b/configs/P1010RDB-PB_NAND_defconfig
@@ -1,6 +1,6 @@
 CONFIG_SPL=y
 CONFIG_TPL=y
 CONFIG_SYS_EXTRA_OPTIONS="P1010RDB_PB,NAND"
-+ST:CONFIG_PPC=y
-+ST:CONFIG_MPC85xx=y
-+ST:CONFIG_TARGET_P1010RDB=y
+CONFIG_PPC=y
+CONFIG_MPC85xx=y
+CONFIG_TARGET_P1010RDB=y