defconfig: 8994: enable CONFIG_DEBUG_SLUB_PANIC_ON

Add the DEBUG_SLUB_PANIC_ON option to KCONFIG preventing
the existing defconfig option from being overwritten
by make config.

This will induce a panic if slab debug catches corruptions
within the padding of a given object.

The intention here is to induce collection of data
immediately after the corruption is detected with
the goal to catch the possible source of the corruption.

Change-Id: Ide0102d0761022c643a761989360ae5c853870a8
Signed-off-by: David Keitel <dkeitel@codeaurora.org>