kbuild: Fix optimization level choice default

The choice containing the CC_OPTIMIZE_FOR_PERFORMANCE symbol
accidentally added a "CONFIG_" prefix when trying to make it the
default, selecting an undefined symbol as the default.

The mistake is harmless here: Since the default symbol is not visible,
the choice falls back on using the visible symbol as the default
instead, which is CC_OPTIMIZE_FOR_PERFORMANCE, as intended.

A patch that makes Kconfig print a warning in this case has been
submitted separately:
http://www.spinics.net/lists/linux-kbuild/msg15566.html

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Author: ulfalizer

init/Kconfig

@@ -1033,7 +1033,7 @@ endif
 
 choice
 	prompt "Compiler optimization level"
-	default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
+	default CC_OPTIMIZE_FOR_PERFORMANCE
 
 config CC_OPTIMIZE_FOR_PERFORMANCE
 	bool "Optimize for performance"