r600/eg: workaround bug with tess shader and dynamic GPRs.

r600/eg: workaround bug with tess shader and dynamic GPRs.

When using tessellation on eg/ni chipsets, we must disable
dynamic GPRs to workaround a hw bug where the GPU hangs
when too many things get queued.

This implements something like the r600 code to emit
the transition between static and dynamic GPRs, and to
statically allocate GPRs when tessellation is enabled.

Signed-off-by: Dave Airlie <airlied@redhat.com>