defconfig: Enable more debug configs on SDXPRAIRIE target

- FREELIST_RANDOM to control the state of the heap and reduce risk
  surface.
- DEBUG_CREDENTIALS to debugging of credential management.
- Enable config to trigger panic on data corruption.
- Enable Panic on Recursive fault.
- Enable GPIO debugfs.

Change-Id: Ie5bcedbb875fda6396d133117bd12b5d0e4da4b5
Signed-off-by: Jeevan Shriram <jshriram@codeaurora.org>