winsys/radeon: move GEM domains out of the drivers into winsys

winsys/radeon: move GEM domains out of the drivers into winsys

The drivers don't need to care about the domains. All they need to set
are the bind and usage flags. This simplifies the winsys too.

This also fixes on r600g:
- fbo-depth-GL_DEPTH_COMPONENT32F-copypixels
- fbo-depth-GL_DEPTH_COMPONENT16-copypixels
- fbo-depth-GL_DEPTH_COMPONENT24-copypixels
- fbo-depth-GL_DEPTH_COMPONENT32-copypixels
- fbo-depth-GL_DEPTH24_STENCIL8-copypixels
I can't explain it.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>