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 <[email protected]>

Author: arve-android

lib/Kconfig.debug

@@ -670,8 +670,9 @@ config DEBUG_LOCKING_API_SELFTESTS
 	  mutexes and rwsems.
 
 config STACKTRACE
-	bool
+	bool "Stacktrace"
 	depends on STACKTRACE_SUPPORT
+	default y
 
 config DEBUG_STACK_USAGE
 	bool "Stack utilization instrumentation"