Doesn't change anything yet, but this will let us more easily add
mapping from dirty gallium state to dirty gen-specific state-groups.

Note that the mapping from shader-state to global state in
fd_context_dirty_shader() optimizes out for release builds.  This
is kind of important, in the next patch we'll want ffs(SOME_CONST)
to optimize away even more.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <mesa/mesa!9581>