defconfig: Disable SLAB_MERGE.

Qcom baseline default disable SLAB_MERGE,
qcom init.qcom.post_boot.sh need to process zspage/zs_handle,
otherwise the following error will occur:
avc denied:{ write } for comm="init.qcom.post_" name="store_user" dev="sysfs" ino=81436
scontext=u:r:vendor_qti_init_shell:s0 tcontext=u:object_r:sysfs:s0 tclass=file permissive=0 pkg=""

Change-Id: I40a5339ba7050ed68626de982802b5c1bad6fd88
Signed-off-by: xiewen3 <xiewen3@motorola.com>
Reviewed-on: https://gerrit.mot.com/2165870
SME-Granted: SME Approvals Granted
SLTApproved: Slta Waiver
Tested-by: Jira Key
Reviewed-by: Xiangpo Zhao <zhaoxp3@motorola.com>
Submit-Approved: Jira Key
Reviewed-by: Wang Wang <wangwang1@lenovo.com>

arch/arm64/configs/vendor/ext_config/moto-bengal.config

@@ -66,3 +66,4 @@ CONFIG_USB_VIDEO_CLASS=y
 # CONFIG_ZRAM_DEDUP is not set
 CONFIG_ION_POOL_FILL_MARK=16
 CONFIG_DEBUG_BUGVERBOSE=n
+# CONFIG_SLAB_MERGE_DEFAULT is not set