[mmalrenderer] Add choice of 3 deinterlace schemes

The Pi firmware can support 3 deinterlace schemes, so report them in renderer, and then pass through settings to firmware.
if this is not meant for sw deinterlacing, you should create new flags. reusing flags creates a lot of confusion. some platforms are capable of doing hw and sw deinterlacing. devs like me who try to maintain a core over various platforms get confused.
same applies to VS_INTERLACEMETHOD_DEINTERLACE