dm-verity's overhead is non-negligible.
As we're optimizing for performance over security, always use
"check_at_most_once".
This feature is available on kernels v4.17 and onwards and is
equivalent to CONFIG_DM_ANDROID_VERITY_AT_MOST_ONCE_DEFAULT_ENABLED
on older kernels.
Change-Id: Ib8b13d8429ac62bb1553ae81a7175d33fdb2e471
Signed-off-by: Juhyung Park <qkrwngud825@gmail.com>