i965/gen6/blorp: Set need_workaround_flush immediately after primitive

i965/gen6/blorp: Set need_workaround_flush immediately after primitive

This patch makes the workaround code in gen6 blorp follow the pattern
established in the regular draw path. It shouldn't result in any
behavioral change.

On gen6, there are two places where we emit 3D_CMD_PRIM: brw_emit_prim()
and gen6_blorp_emit_primitive().  brw_emit_prim() sets
need_workaround_flush immediately after emitting the primitive, but
blorp does not. Blorp sets need_workaround_flush at the bottom of
brw_blorp_exec().

This patch moves the need_workaround_flush from brw_blorp_exec() to
gen6_blorp_emit_primitive().  There is no need to set
need_workaround_flush in gen7_blorp_emit_primitive() because the
workaround applies only to gen6.

Reviewed-by: Paul Berry <stereotype441@gmail.com>
Signed-off-by: Chad Versace <chad.versace@linux.intel.com>