anv/cmd_buffer: Re-emit the pipeline at every subpass

If we ever hit this edge-case, it can theoretically cause problem for
CNL because we could end up changing render targets without re-emitting
3DSTATE_MULTISAMPLE which is part of the pipeline.  Just get rid of the
edge case.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
(cherry picked from commit 97938dac)