i965: Set up swizzling of shadow compare results for GL_DEPTH_TEXTURE_MODE.

The brw_wm_surface_state.c handling of GL_DEPTH_TEXTURE_MODE doesn't
apply to shadow compares, which always return an intensity value.  The
texture swizzles can do the job for us.

Fixes:
glsl1-shadow2D(): 1
glsl1-shadow2D(): 3
1 file changed