implement incremental YUV conversion with pref SQ
implement access to 32bit VRAM with pref SQ
init YUV converter when TA_YUV_TEX_CTRL is set
set FIFO available space to 256 through SB_TFREM reg
fake FIFO status through SB_FFST reg
Originally ported from nullDC to libretro in commits:
2fa562db1b46c52b663b3dd4bb33a64907357458
f8eb58ac16a9e5adf662b99be5d00729264808e0
Modified for use w/ reicast per-game configuration