hwc: bring back fb support for primary for mdp303.

Change-Id: I98cf0fdae6b9b1100c97ac319ab1c321f55fe507
hwc: Get the retire fence from the MDP driver
Get the retire fence separately instead of duplicating the
release fence.

Bug: 9319776
Change-Id: Iacb773c2d94f635e27a7b355d399cb2e36dac2a5
Signed-off-by: Iliyan Malchev <malchev@google.com>