Allow CONFIG_STACKTRACE to be enabled by itself.

This allows us to get a kernel stacktrace for a thread though /proc.
Also enable it by default.

Change-Id: If8c21cd02feaf9863f4841ace524fa30c7328d49
Signed-off-by: Arve Hjønnevåg <arve@android.com>
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index dd373c8..c6b006a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -667,8 +667,9 @@
 	  mutexes and rwsems.
 
 config STACKTRACE
-	bool
+	bool "Stacktrace"
 	depends on STACKTRACE_SUPPORT
+	default y
 
 config DEBUG_STACK_USAGE
 	bool "Stack utilization instrumentation"