i965: Pass start_offset to brw_set_uip_jip().

i965: Pass start_offset to brw_set_uip_jip().

Without this, we would pass over the instructions in the SIMD8 program
(which is located earlier in the buffer) when brw_set_uip_jip() is
called to handle the SIMD16 program.

The assertion about compacted control flow was bogus: halt, cont, break
cannot be compacted because they have both JIP and UIP. Instead, we
should never see a compacted instruction in this code at all.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>