nv30, nv40: non-trivially unify nv[34]0_state_emit.c

nv30, nv40: non-trivially unify nv[34]0_state_emit.c

The files are the same except for swtnl support on nv40 and for
texture cache flushing on nv40.

Unify them, and use a macro to define 4 versions of render_states,
for all combinations of nvfx and hwtnl/swtnl.