Set stencil ref value to 255 (8 bitplanes) 2^8-1=255

Since we're using 0xFF to disable the stencil mask and we have 8 bitplanes , try to set it to 2^8-1=255

This fixes NBA Live 06

-Before
![screen00028](https://f.cloud.github.com/assets/3000282/1306741/803d35f6-31b4-11e3-967f-7a178123554c.jpg)

-After
![screen00027](https://f.cloud.github.com/assets/3000282/1306742/835de316-31b4-11e3-9dc0-4325b85cdfb0.jpg)