ChibiOS: fix crash on auto detection

ChibiOS: fix crash on auto detection

The detection framework assumes rtos->symbols is dynamically allocated,
an assumption that the ChibiOS variant breaks by providing a raw statically
allocated symbol list.

Change-Id: I379bcc2af99006912608ddd3f646ff7085606f47
Signed-off-by: Richard Braun <rbraun@sceen.net>
Reviewed-on: http://openocd.zylin.com/2597
Tested-by: jenkins
Reviewed-by: Stian Skjelstad <stian@nixia.no>
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-by: Paul Fertser <fercerpav@gmail.com>