correct the zpos and capability of layers
If a TDM backend support PP, when video is playing, the display
server normally will convert a video image with PP and show it
to a GRAPHIC layer. If a GRAPHIC layer fully supports scaling,
rotating and various color formats, the display server will show
a video image to a GRAPHIC layer without converting.
However, some hardware vendors want to handle a video image directly
inside of their TDM backend module. If a TDM backend module offer
VIDEO layers, the display server will pass a video image to the TDM
backend module without any modification. No scaling, no rotating.
And also, the display server won’t check video formats too. Then a
TDM backend module has the responsibility to display a video image
on the screen.
Change-Id: I932916f756291a40ddb8b19048d065769e8072e8