defconfig: arm64: SLAB_FREELIST_RANDOM for sdm855.

Enable SLAB_FREELIST_RANDOM and SLAB_FREELIST_HARDENED to
randomize the SLAB freelist for kernel harding.

Change-Id: I6fb40f5512d24242937f3476f1b6e6067665e2f3
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>