lib/Kconfig.debug: enable RUNTIME_TESTING_MENU

Commit d3deafaa8b5c ("lib/: make RUNTIME_TESTS a menuconfig to ease
disabling it all") causes a regression when using runtime tests due to
it defaults RUNTIME_TESTING_MENU to not set.

Link: http://lkml.kernel.org/r/20180214133015.10090-1-anders.roxell@linaro.org
Fixes: d3deafaa8b5c ("lib/: make RUNTIME_TESTS a menuconfig to easedisabling it all")
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Cc: Vincent Legoll <vincent.legoll@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 6088408..64155e3 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1642,6 +1642,7 @@
 
 menuconfig RUNTIME_TESTING_MENU
 	bool "Runtime Testing"
+	def_bool y
 
 if RUNTIME_TESTING_MENU