hwc: Reset FB Z order to -1 instead of 0
In Video-only mode FB Z-order of 0 was being used, incorrectly,
because the value was reset to 0 and wasn't changed subsequently.
Reset to -1 to prevent this. Any MDP comp strategy that needs to use
FB should set it's Z order appropriately.
If cache based mode has no MDP comp layers, fail so that other
strategies can be used, rather than succeeding with FB Z as 0, which
will at most allow GPU comp to be used.
Change-Id: Ifdae2cd5f8d8ff0e10447b1fed6ee1671260f311
1 file changed