arm64: openeuler_defconfig: turn on Amazon ENA ethernet driver

This driver is turned on on x86_64 already. Let's turn it on for arm64
as AWS supports ENA device on their arm64 instance.

Signed-off-by: Kai Liu <kai.liu@suse.com>
Signed-off-by: Guoqing Jiang <guoqing.jiang@suse.com>