ANDROID dm-verity: fix root device init timing issue.

[Detail] Depending on storage initialization speed, root block device
may not be ready when configuring it to enable dm-verity, this causes
dm-verity critical error and system reboots. To mitigate this issue,
we added retry and timeout mechanism, where timeout value is 2s.

Bug: 68731686
Test: We can reproduce the issue before we apply this patch but we
cannot reproduce the issue after we apply this patch. Device can
always boot up to homescreen after we apply this patch.

Change-Id: Ia360a63c5c90f7d81ef1465f308995fb69406a83
Signed-off-by: Iris Chang <iris.chang@mediatek.com>