i965: Remove the INTEL_OLD_VS option.

i965: Remove the INTEL_OLD_VS option.

Now that we no longer generate Mesa IR from GLSL IR, it's impossible to
use the old vertex shader backend for GLSL programs.  There's simply no
Mesa IR to codegen from.

Any attempt to do so would result in immediate GPU hangs, presumably due
to the driver uploading an empty program with no EOT message.

NOTE: This is a candidate for the 8.0 branch.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>