nv50: allow using inline vertex data submit when gl_VertexID is used

nv50: allow using inline vertex data submit when gl_VertexID is used

The hardware can actually generates vertexid when vertices come from
a client-side buffer like when glDrawElements is used.

This doesn't fix (or break) any piglit tests but it improves the
previous attempt of Ilia (c830d19 "nv50: avoid using inline vertex
data submit when gl_VertexID is used")

The only disadvantage is that only works on G84+, but we don't really
care of that weird and old NV50 chipset.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>