radeonsi: take reference glsl types for compile threads

radeonsi: take reference glsl types for compile threads

An application quitting before the destroying its GL context and
binding a NULL context might still have a radeonsi compiler thread
running and potentially still accessing the types.

Therefore take a reference for the duration of the threads' lifetime.

v2: Only ref the glsl types, the builtins should be used by the time
    shader data gets to a gallium driver.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>