i965: Fix haswell_upload_cut_index when there's no index buffer.

i965: Fix haswell_upload_cut_index when there's no index buffer.

brw->ib.type is reset to -1 at the start of each batch.  If there's no
index buffer, it won't get updated to a sensible value, resulting in
_mesa_primitive_restart_index's "Invalid index buffer type" assertion
tripping.

Fixes a regression since 7c87a3b5dac118697a9b67caa7b6d5cab60f316d.

NOTE: This is a candidate for the 9.1 branch (and should be squashed).
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=65195
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>