freedreno/a3xx: re-emit shaders on variant change

freedreno/a3xx: re-emit shaders on variant change

We need to keep track if a state change other than frag/vert shader
state will trigger us to need a different shader variant, and if
necessary mark the appropriate shader state as dirty.  Otherwise we will
forget to re-emit the shader state.

Signed-off-by: Rob Clark <robclark@freedesktop.org>