Remove legacy/O/O-MR1 matrices.

Devices with legacy/O/O-MR1 VINTF won't be able to
update to Android S. Devices launching with pre-O,
O, or O-MR1 will need to update its VINTF to P and
above to work with Android S.

Test: builds
Bug: 163419744
Bug: 171260360
Bug: 171260613
Bug: 171260670
Bug: 171260715
Change-Id: I2a65f5a24c0731df9c4247bf9dd2616c2279042f