OWNERS: update owner information

I will change to another assignment soon so transfer the ownership to
Thu Nguyen.
Also add Dung Cao as reviewer to review commits related to SSIF.

Change-Id: Ic965143b7b9adaae258d1e4a23f48a29fa033649
Signed-off-by: Thang Q. Nguyen <thang@os.amperecomputing.com>
1 file changed