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

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

nv30_draw.c is a stub.

This patch makes both nv30 and nv40 use the nv40 swtnl path.

Note that this doesn't actually work on nv30 because the vertex program is
encoded in the nv40-only layout.

However, swtnl was unimplemented before on nv30, so this is not a regression.
Furthermore, a patch to fix this is available near the end of the patchset.