config: Enable the config option of the etmem feature

euleros inclusion
category: feature
feature: etmem
bugzilla: 49889

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Enable etmem feature config option.
set default value of CONFIG_ETMEM_SCAN and
CONFIG_ETMEM_SWAP.

Before using the etmem feature, need to insert
etmem_scan.ko and etmem_swap.ko first.

Signed-off-by: liubo <liubo254@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Reviewed-by: Jing <Xiangfeng&lt;jingxiangfeng@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>